There were 184 rape allegations in 2014, up from 33 in 2009, the National Crime Agency (NCA) said.
It said 85 per cent of the rape victims were women and of these, 42 per cent were aged 20 to 29 and 24 per cent were aged between 40 and 49.
The agency said it was concerned the number may be under- reported.
More than nine million people in the UK have signed up to dating websites, the BBC reported.
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"This initial work clearly raises a lot of questions and we will be working with academia to build a more complete picture," it quoted Sutton as saying.
"Our aim here is to make people aware of the potential danger, so they can be better prepared and make the choices that are right for them.
"Sexual assault is a crime, full stop, and we want victims to feel confident reporting it to the police," Sutton said.
"Even one incident of harm is one too many.
"The NCA is right to look at what happens online and the ODA are already working with them in getting the right messages out to people."
Earlier this month, security firm Symantec said online daters fell victim to blackmail, were subjected to revenge porn and were tricked by people who assumed fake identities to steal cash.