In a survey conducted by a major condom brand, 65 per cent said that they would never cheat on their partner.
However, the poll of more than 12,000 people online showed that 45 per cent of have enjoyed phone sex.
"It all makes pretty steamy reading," a major newspaper quoted the condom brand's spokeswoman as saying.
The study also revealed that 14 per cent of Brits secretly think about their ex when they are having sex and five per cent think about a workmate.
The average Brit now has sex three to four times a week and has slept with between two and five people.
A promiscuous two per cent claim to have bedded more than 100 lovers.
In the survey, 22 per cent confessed to never using a condom.