How to deal with a difficult colleague: dealing with bullies at work

A quarter of UK workers say they’ve experienced conflict or abuse at work in the past 12 months, according to the CIPD’s 2024 study of more than 5,000 employees. Almost half of those affected said they just let it go. The colleague who undermines you in meetings, the manager who picks at your work in front of the team, the teammate who freezes you out: this guide covers how to handle them, what UK law gives you to work with, and when to stop trying to repair the relationship and start protecting yourself.

Why this matters: the real cost of a difficult colleague

Toxic behaviour costs UK businesses an estimated £18 billion a year, with about 17 million working days lost to bullying and related conflict. Employers feel that hit. Individuals carry it too, as anxiety, lost sleep, lower confidence, and resignations that often weren’t planned.

The CIPD’s 2024 bullying and harassment report found that 25% of UK employees had experienced conflict or abuse in the past year, and 15% had been bullied within the last three years. 47% of those affected said they did nothing about it. Only 36% of those who did raise an issue felt it had been fully resolved.

The mental health bill is even larger. Deloitte’s 2024 workplace wellbeing study put the cost of poor mental health to UK employers at £51 billion a year, with 63% of workers showing at least one sign of burnout. A 2024 cross-sectional study published in the British Journal of General Practice found that workplace bullying was strongly associated with common mental disorders, sharply lower confidence, and weaker social connections.

The numbers translate into real days, real pay packets, real lives. If you’re reading this because a particular person is making your job miserable, the data is simply confirmation that you’re not alone, and that the cost of doing nothing is rarely zero.

Difficult behaviour versus bullying: where the line sits

Difficult behaviour and bullying overlap. They aren’t the same thing.

Bullying has no specific statutory definition in the UK, but ACAS describes it as offensive, intimidating, malicious or insulting behaviour, or an abuse or misuse of power that undermines, humiliates, or causes physical or emotional harm. The keyword is pattern. A single tense meeting isn’t bullying. Repeated belittling over weeks or months is.

Harassment carries a legal definition. Under the Equality Act 2010, harassment is unwanted conduct related to a protected characteristic (age, disability, gender reassignment, marriage and civil partnership, pregnancy and maternity, race, religion or belief, sex, or sexual orientation) that violates a person’s dignity or creates an intimidating, hostile, degrading, humiliating, or offensive environment. Harassment can be a single incident. It is unlawful, and employers have a duty to protect staff from it.

Some difficult colleagues are tactless, stressed, or under-trained. Others are causing real harm. The strategies below begin with the assumption that a colleague is difficult, then escalate as the behaviour does.

Practical strategies for dealing with a difficult colleague

Get clear on your own goals first

You’re at work to do a job and get paid. Friendship at work is a bonus, not a deliverable. Before you respond to a difficult colleague, write down what you actually want: a meeting handed off, an email tone you can live with, a project signed off without friction.

The clearer your goal, the less likely you are to get pulled into the drama. The Thomas-Kilmann Conflict Mode Instrument, used in HR and management training across the UK, calls this collaborating: addressing the issue directly while preserving enough of the relationship to keep working.

Work out what’s driving the behaviour.

People rarely act out for no reason. A teammate who’s snappy in the mornings may be caring for a parent. A colleague who treats every project as a competition may be on a performance plan you don’t know about. None of that excuses bad behaviour. It does change how you respond.

Ask yourself: what changed recently? Is this person under pressure from above? Are they new to the team and overcompensating? Skip the amateur psychology and gather just enough context to stop taking it personally.

Audit your own reactions.

Office life is bearable or unbearable depending on how you respond to friction. A colleague who asks ten questions before lunch isn’t difficult; they’re being thorough. The difficulty sometimes sits in the eye of the beholder.

A useful test: would a colleague you respect describe this person the way you do? If three out of five people on your team find them tricky, the problem is them. If it’s only you, the work is partly internal. Either answer is useful.

Start the day in neutral.

Body language and tone are read before words are. Walk in, greet everyone, including the difficult colleague, and don’t telegraph that you’re bracing for a fight. Skip performed cheerfully. Refusing to broadcast resentment is enough.

That stance denies difficult people the reaction they’re trained to look for, which is often what calms the day down.

Speak up instead of stewing.

If a colleague’s behaviour is blocking your work, the longer you wait to raise it, the harder it gets. Most workplace conflict festers in silence. The CIPD’s 2024 data shows that 47% of employees experiencing conflict at work say they just let it go, and only 36% of those who do raise an issue feel it has been resolved. Early calm conversations work better than late angry ones.

A simple structure helps. Ask for a private word. Name the specific behaviour. Name its impact on the work. Ask for a change. “When you cut across me in standups, I lose the chance to flag blockers. Can we agree to let each person finish?” That sentence does more than three weeks of complaining to other people.

Use a script, not a speech.

Difficult conversations go off the rails when you ad-lib. Plan three sentences before you walk in:

The fact (what they did, when)
The impact (on your work or the team’s work)
The request (what you’d like to change)

Restorative conversation frameworks, used in UK schools and many NHS trusts, follow the same logic. Keep emotions low. Keep specifics high. If the other person becomes defensive, hold the line. “I hear that. I’d still like to agree on how we handle this next time” is a phrase worth memorising.

Pick your battles deliberately.

Not every irritation is worth a meeting. A snippy email on a Friday afternoon is not the hill to die on. A colleague who consistently takes credit for your work is. Save the formal conversations for patterns.

Steer clear of the people at work who gossip, score-settle, or pick fights with everyone. The less time you spend with them, the steadier your day. You aren’t required to win them over. Most of them aren’t trying to be won.

Keep a paper trail

If a colleague’s behaviour is heading anywhere near a grievance, you’ll need evidence. Save emails. Note dates, times, what was said, and who was present. Use one document, stored privately, ideally on a personal device rather than a work laptop.

A paper trail turns “I felt belittled” into “On 14 March, in front of three colleagues, X said Y.” HR can act on the second. They struggle with the first.

Don’t talk about colleagues with colleagues.

Office gossip is a trap. The colleague you confide in this week is the one who repeats your words back to the wrong person next week. Vent to a partner, a friend outside work, or a therapist. Keep work conversations about work.

If you need to escalate, go to HR or your line manager, not the kitchen.

When a difficult colleague is actually a bully

Look for patterns over time. ACAS guidance lists examples of bullying behaviour that include spreading malicious rumours, ridiculing or demeaning someone, unfair treatment, overbearing supervision, exclusion, and threats about job security. Where these are repeated over weeks or months and aimed at one person, the situation has moved from a difficult colleague to workplace bullying.

Three things matter once you’re at this point.

First, follow your employer’s policy. Most UK employers will have a bullying and harassment policy. Find it on the intranet or ask HR for a copy.

Second, try the informal route first if it’s safe to do so. ACAS guidance is clear that informal resolution, often with HR support, is quicker and less damaging than a formal grievance. A trained workplace mediator can sometimes settle in an hour what months of escalation can’t.

Third, raise a formal grievance in writing if informal routes fail or are inappropriate. This applies where the behaviour is severe, where retaliation is likely, or where the conduct amounts to harassment under the Equality Act 2010. The ACAS Code of Practice on Disciplinary and Grievance Procedures, in force since 2015, sets the minimum standard your employer is expected to meet: a written grievance, a hearing, the right to be accompanied, a written outcome, and a right of appeal. Tribunals can adjust awards by up to 25% if employers fail to follow them.

If the conduct involves harassment linked to a protected characteristic, constructive dismissal, or whistleblowing, speak to a solicitor or to ACAS directly on the free helpline (0300 123 1100). Many employment law firms offer a free initial consultation. Citizens’ Advice and trade unions also provide free guidance. Most tribunal claims must be filed within three months less one day of the act complained of, so the clock matters.

Protecting your mental health

Workplace bullying is associated with anxiety, depression, sleep loss, and, in severe cases, suicidal ideation. If your job is starting to affect your mental health, the workplace is no longer the only thing you’re dealing with.

A few practical steps:

Talk to your GP. They can sign you off if needed, refer you for talking therapy, or put you in touch with NHS Talking Therapies (free in England, self-referral allowed in most areas).
Use occupational health if your employer has it. They report to the employer, but their clinical assessments are confidential and can carry real weight in a grievance or tribunal.
Mind and Mental Health UK both run free information lines and online resources covering work-related stress and bullying.
If you’re in crisis, the Samaritans are available 24/7 on 116 123 (free) or by email. The Shout text line (text 85258) is also free and confidential.

You don’t owe a job to your well-being. If leaving is the only route back to health, leaving is the right call. Plenty of people, including many who don’t talk about it publicly, have had to make that decision.

What to do if your manager is a difficult colleague

Bad managers are the most common reason people quit. Research from the Chartered Management Institute found that one in three UK workers had left a job because of poor management, and that half of those rating their manager as ineffective planned to resign within the year.

If your manager is the problem, the playbook shifts slightly.

You can still ask for a calm conversation. The power imbalance changes the stakes, so use the same script: fact, impact, request. Put a summary in writing afterwards. A short email along the lines of “thanks for the chat, just confirming what we agreed” creates a record that becomes useful later.

Skip-level conversations are a legitimate option in most organisations. If your manager’s manager is approachable, ask for a confidential coffee and frame it as asking for guidance: “I’m finding the working relationship hard. What’s your advice?”

If the behaviour amounts to bullying or harassment, follow the formal grievance route described above. Most employers expect employees to raise concerns with someone other than the alleged perpetrator, and ACAS guidance specifically allows for grievances to be raised with the next level of management when the immediate manager is involved.

If HR is reluctant or aligned with the manager (a real risk, particularly in smaller organisations), an external employment solicitor, a trade union, or ACAS can advise on next steps before you put anything formal in writing.

Frequently asked questions

What counts as workplace bullying in the UK?

ACAS defines workplace bullying as offensive, intimidating, malicious, or insulting behaviour, or an abuse or misuse of power that undermines or humiliates someone. It’s generally a pattern rather than a single incident. Examples include spreading rumours, public humiliation, exclusion, unfair treatment, and overbearing supervision. Bullying isn’t directly outlawed by UK statute, but related harassment is illegal under the Equality Act 2010.

Can I be sacked for raising a grievance against a colleague?

Workers who raise a genuine grievance, particularly one involving discrimination or whistleblowing, are protected from retaliation under UK law. A dismissal connected to a protected disclosure or to making a discrimination complaint can be automatically unfair, and the usual two-year qualifying period for unfair dismissal may not apply. Keep written records and seek advice from ACAS or a solicitor early.

Should I leave my job because of a difficult colleague?

Possibly, though it’s worth treating resignation as a last resort. Try the informal conversation, the grievance route, and the occupational health referral first. If your mental health is at risk and the employer won’t act, leaving may be the safer option. A constructive dismissal claim is sometimes available where an employer’s failure to address serious bullying has broken the implied trust of the employment contract. Take legal advice before resigning.

How do I document workplace bullying?

Keep a contemporaneous log: date, time, location, exactly what was said or done, and who was present. Save emails, screenshots, Teams or Slack messages, and any witness statements. Store the file outside work systems on a personal device. Note the impact on your work and health as you go, including GP visits or occupational health referrals. Detailed, dated records carry far more weight than recalled impressions in any internal or tribunal process.

What’s the difference between bullying and harassment?

Bullying is a workplace term in the UK with no specific statutory definition. Harassment is defined in the Equality Act 2010 and applies when the unwanted conduct relates to a protected characteristic such as age, sex, race, disability, or religion. Harassment can be a single incident. Bullying generally has to be a repeated pattern. Both can be raised through a grievance, though harassment opens legal claims that bullying alone may not.

Where can I get free help in the UK?

ACAS runs a free confidential helpline on 0300 123 1100, open Monday to Friday. Citizens Advice provides free guidance on employment matters in person, online, and by phone. Mind and Mental Health UK offer free information lines for the mental health impact of workplace bullying. Most trade unions provide legal support to members at no extra cost, and many employment solicitors offer a free initial consultation.

The bottom line

Difficult colleagues are part of working life. Bullies are a more serious problem, and the difference comes down to pattern and power. Get clear on your goals, document what’s happening, have the calm conversation early, and know your rights under the ACAS Code and the Equality Act 2010. If the work is costing you your health, talk to your GP, ring ACAS, and remember that no job is worth your wellbeing.

How To Deal With A Difficult Colleague? Dealing With Bullies At Work