The most favoured way of keeping tabs on a partner is checking their text messages, with more than half (53 percent) of those questioned admitting sneaking a peek.

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For young people aged 25 to 34 the number shoots up to a startling 77 percent.

The second most popular way of finding out if a partner has been a love-cheat is to read their e-mails 42 percent told the UK Undercover Survey that they had carried out such a ploy.

The third is the old-fashioned method of rummaging through a partner's pockets, (39 percent), the survey found this was technique was particularly popular with women.

But men weren't in the clear. They prefer to break another great unspoken rule - reading their partner's diary.

And neither is the spoken word safe, with many people admitting to listening on conversations their other halves believed would be confidential.

About one in three (31 percent) of those questioned in the survey, commissioned by the Science Museum in London, for its Science of Spying exhibition, said they covertly listened in on their partner's private conversations.

High-tech spying

At the paranoid end of the spectrum, a small number of the 1,129 people questioned said they had even secretly recorded their partner's telephone conversations, using dictaphones or other such taping devices.

Surprisingly, this method was the most popular with the over-55s age group not usually known for being tech-savvy. One in 20 (5 percent) admitted to it.

This age group also included people who used other hi-tech devices to keep an electronic eye on their partners, such as using webcams to watch them while they were at work, or GSM tracking devices to follow them in their cars.

Almost one in 10 (9 percent) fancied themselves as private eyes, following their partners from a distance to check that they weren't meeting with a secret lover.

Commenting on the survey's findings, former spy Harry Ferguson, once an agent with the UK's MI6 secret service, said: "Everyone has the ability to be a bit of a spy every now and again. You don't need to have James Bond's gadgets to enter the world of espionage."