Infidelity Statistics in the UK (2025)

Key takeaways

• Prevalence: Around 1 in 5 British adults have at some point admitted to cheating on a partner in survey research. Men and women report similar lifetime rates (c. 20% vs 19%). (YouGov)
• Attitudes: 57% of the British public say extra-marital sex is “always wrong”—a figure remarkably stable since the 1980s. (National Centre for Social Research)
• Acceptability & divorce: In a GB poll, 78% say infidelity is a good enough reason for divorce. (YouGov)
• Who people cheat with: Among those who admit affairs, common partners include friends (43%) and work colleagues (38%). (YouGov)
• Law changed in England & Wales: Since 6 April 2022, divorces proceed under no-fault rules; formal “grounds” like adultery are no longer cited, so divorce statistics can’t be used as a clean proxy for infidelity. (Office for National Statistics)

What counts as “infidelity”?

Researchers and the public draw boundaries differently:

• Adultery (a legal term) historically meant a married person having sexual intercourse outside marriage.
• Infidelity/cheating (a social term) ranges from sexual contact to emotional or online behaviours (e.g., joining dating apps, secret messaging). In past polling, women were more likely than men to class signing up to dating apps as cheating (67% of women vs 43% of men), underscoring definitional variation by gender. (YouGov)
• Around holidays the public’s lines can even shift—e.g., a minority said a “mistletoe kiss” muddies whether snogging counts as cheating—illustrating social context effects. (YouGov)

Why the definition matters: Different cut-offs change reported prevalence. UK social surveys therefore often measure attitudes and relationship outcomes alongside (or instead of) direct admissions.

How common is infidelity in Britain?

Self-reported lifetime cheating

The best-known national polling finds about 20% of British adults say they have had an affair at some point (2015 YouGov omnibus). Men and women reported similar lifetime prevalence (20% vs 19%). (YouGov)

Caveat: Admitting rule-breaking is sensitive, so these figures are likely lower-bound estimates. Differences in question wording and whether “emotional” behaviours are included also affect results.

Who do people cheat with?

Among those who admitted cheating in that survey, the most common third parties were friends (43%), work colleagues (38%), strangers (18%), ex-partners (12%), and neighbours (8%). (YouGov)

Cheating as a reason relationships end

In the gold-standard Natsal-3 study of Britain’s sexual behaviours, people who had recently experienced a partnership breakdown often cited unfaithfulness/adultery among leading reasons—18% of men and 24% of women (along with “grew apart” and “arguments”). This speaks to the salience of infidelity in relationship dissolution. (LSHTM Research Online, Mahidol University, ResearchGate)

What do Britons think about infidelity?

• Moral stance: The British Social Attitudes series reports that 57% now say extra-marital sex is “always wrong”, barely changed from 58% in 1983. Unlike attitudes to premarital sex or same-sex relationships—which liberalised sharply—views on infidelity have not. (National Centre for Social Research)
• Grounds for divorce: 78% of GB adults say cheating is sufficient reason to divorce (YouGov, Jan 2022). (YouGov)

Divorce, adultery and the law (why divorce stats don’t equal cheating rates)

• England & Wales: The Divorce, Dissolution and Separation Act 2020 (in force 6 April 2022) introduced no-fault divorce and removed the need to state grounds (formerly “facts” such as adultery or unreasonable behaviour). As a result, official divorce counts no longer record adultery as a reason. In 2023 there were 102,678 divorces and the median duration of opposite-sex marriages at divorce was 12.7 years. (Office for National Statistics)
• Scotland & Northern Ireland: Grounds still exist in statute. In Scotland, irretrievable breakdown can be established by adultery, behaviour, or separation (1–2 years); most actions proceed on separation rather than fault. NI still lists adultery among grounds, with policy consultations ongoing. (These legal frameworks differ from E&W, hence UK-wide comparisons using “adultery” in court data are not straightforward.) (Scottish Government, Brodies LLP, Department of Finance)

Digital and “grey-area” behaviours

Technology blurs boundaries. Older GB polls showed disagreement over whether joining dating sites/apps while partnered is itself cheating (women 67%, men 43% saying yes). Social norms also flex with context (e.g., festive “mistletoe” scenarios). These nuances partly explain why prevalence numbers vary between studies. (YouGov)

Trends to watch in 2025

• Stable moral disapproval: Decades-long stability in BSA’s “always wrong” measure suggests enduring social condemnation of infidelity, even as other sexual norms liberalised. (National Centre for Social Research)
• Measurement changes post-2022: With no-fault divorce in England & Wales, administrative data no longer tag adultery—pushing analysts towards surveys (YouGov, BSA, Natsal) for insight. (Office for National Statistics)

Methodology notes (why figures differ)

• Under-reporting & wording effects: People may under-admit cheating; questions that include emotional or online behaviours yield higher rates than those asking only about sexual intercourse.
• Sampling: National probability surveys (e.g., BSA, Natsal) are stronger for attitudes & correlates; commercial omnibus polls (YouGov) provide timely snapshots of self-reported behaviour but may use different frames. (National Centre for Social Research, LSHTM Research Online)

Frequently asked questions

Is cheating becoming more common?
There’s no definitive UK time-series on behaviour. What we do know: attitudes to infidelity have stayed consistently negative, while divorce administration no longer records adultery in England & Wales—so we rely on surveys rather than court data for trends. (National Centre for Social Research, Office for National Statistics)

Do men cheat more than women?
In the 2015 YouGov survey, lifetime cheating reports were similar (men 20%, women 19%), though motives and who they cheated with differed. (YouGov)

Is infidelity mainly physical?
Not necessarily. UK polling shows disagreement over whether joining dating apps or other online behaviours count as cheating—one reason researchers often separate sexual, emotional, and online infidelity. (YouGov)

Sources

• YouGov (GB) – self-reported affairs; attitudes to cheating and divorce. (YouGov)
• British Social Attitudes 40 (NatCen) – long-run moral attitudes; 2022 wave: 57% “always wrong” on extra-marital sex. (National Centre for Social Research)
• Natsal-3 (peer-reviewed outputs) – reasons for relationship breakdown include unfaithfulness/adultery (men 18%, women 24%). (LSHTM Research Online, Mahidol University)
• ONS (England & Wales) – divorce counts, rates, no-fault implementation details (2023 bulletin). (Office for National Statistics)
• Scottish Government & NI policy pages – legal context for grounds in Scotland and Northern Ireland. (Scottish Government, Department of Finance)

Bottom line

• The best single UK number for lifetime cheating remains ~20%, with strong, stable social disapproval (57% “always wrong”).
• After no-fault divorce in England & Wales, surveys—not court records—are the primary lens on infidelity.
• Statistics vary with definitions: whether you count emotional and online behaviours changes the picture considerably. (YouGov, National Centre for Social Research, Office for National Statistics)