The number of rape allegations linked to online dating websites has increased sixfold in five years, according to Britain’s leading crime-fighting body.

National Crime Agency (NCA) figures show 184 people made allegations they were raped by someone they met online in 2014 – up from 33 in 2009.

Rape tends to be under-reported and those attacked by people they meet online may be less likely to come forward, meaning the actual number of attacks could be 10 times higher, the NCA warned.

Sean Sutton, head of the NCA's Serious Crimes Analysis Section, said: “Part of our campaign is to encourage people to come forward. Our message is the police will take them seriously and deal with them sympathetically."

"You can't see a stranger rapist coming; they are going to be charming potentially they are going to be persuasive," he said.

"If you think you can see one from a distance or even up front, you can't - that's the issue."

More than nine million Britons have signed up to dating websites and the NCA is advising users to be more careful.

Some 85% of stranger rape victims are women of which 42% were aged between 20 and 29 and 24% between 40 and 49.

George Kidd, chief executive of the Online Dating Association, which is supporting the campaign, said: "Sexual assault or abuse is never acceptable. 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."

The news comes after an investigation revealed alleged crimes involving dating apps Tinder and Grindr increased sevenfold between 2013 and 2015.