A survey commissioned by That's Life magazine and published Friday says nearly one woman in two has searched her husband's pockets or read his mobile phone messages without his knowledge.
Entitled the National Scruples and Lies Survey, it says if women had an extramarital affair and became pregnant, they would not tell the husband that the baby was someone else's.
Nearly a third of women say if they wanted a baby and their partner did not, they would lie about using contraception.
In fact, one woman in ten has even followed her husband to find out what he is doing, according to the survey
Seventy per cent admitted that they would get drunk at the office Christmas party.
And 22 per cent said they called in sick following the party so they could stay in bed with their new man.
Twelve per cent said they would dabble in drugs.
That's Life questioned 5,000 women across the UK with an average age of 38 for the survey.