The survey, published in the US journal Sexuality Research and Social Policy, is alarming for those who push the safe sex message - particularly as chlamydia and HIV infection rates in Australia are now at a 10-year high.

The US study, which surveyed 568 women, also found 27 per cent of respondents performed oral sex on the first date.

Felicity Percival, editor of Women’s Health magazine, said the results were worrying but not surprising.

“People do feel more comfortable with each other when they’ve had lots of conversations online, whether it’s through, Online Dating, Facebook, or any online social network,” she said.

“If you think ‘I know that person, I’m sure they’re safe’, you’re less likely to use a condom.”

Ms Percival said that in general, women were “holding out more” and that the “12 date rule” was becoming popular, but when talking to someone online over a period of time, it was easy to be lulled into a false sense of security.

“Just because you talk to someone online does not mean you know them, and doesn’t mean they’re free of genital warts or herpes,” she said.

“You need to raise these issues with that person before you meet them. You should keep sex sacred, at least for the first few times you meet them.

“It’s really important to get the safe sex message out there, whether you meet in a bar or online.”