One in five of all married couples spy on each other's emails and text messages to ensure they are not cheating, say Oxford University researchers.

And 13 percent of those surveyed have confessed to checking up on the browser's history to find out what their partner had been surfing.

While many couples said the internet was useful for maintaining a relationship, they also admitted it could be a threat by opening up the opportunity for "online infidelity".

Unsurprisingly, 97 percent of respondents would be unhappy if their partner fell in love with someone else via the internet and 92 percent would not be pleased if their other half disclosed intimate details of their relationship to others.

When it comes to visiting adult sites, however, men and women have slightly different views on the matter, with men more likely to accept such behavior in their partner than women.