During the survey conducted by Omio.com, two thirds of the respondents admitted that they snoop into the phones while their lovers are busy in the bathroom.
"The mobile phone has created a culture of suspicion," the Daily Star quoted Matt Wheeler of Omio.com as saying.
"A withheld number, a SIM card full of 'business contacts' and the ex-girlfriend whose number is still stored in his phone - it doesn't take much for many of us to give in to that uncontrollable urge to snoop," he added.
One in ten people surveyed also confessed that they had a second phone or SIM card for their "bit on the side".
Six out of 10 said that they had sent sexually explicit text and 16 per cent had used their phone to film themselves, or someone else, having sex.