Figures from the Home Office show police believe "no crime" took place following 13 per cent of rape complaints.

In contrast, allegations are not investigated in just two per cent of reported burglaries, three per cent of drugs complaints, five per cent of robberies and six per cent of non-sexual assaults.

Earlier this year, a study by the Criminal Justice Joint Inspection team found pressure to keep recorded cases to a "minimum" may lead forces to write off too many allegations as "no crime" incidents.

The data comes amid fresh controversy over the high-profile allegations of sexual assault facing Julian Assange, the founder of Wikileaks - accusations that he strongly denies.

Mr Assange is currently holed up in the Ecuadorian embassy fighting extradition to Sweden where he is wanted for questioning over two incidents.

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Last night, one of his supporters sparked anger by naming one of the women involved in the sexual assault claims on the BBC.

Craig Murray, a former UK ambassador to Uzbekistan and a human rights advocate, also raised questions about "the conduct of these women".

He said: "I think incidents which are dubious themselves as to what has happened, and Julian Assange has denied the accusations against him, are being seized on as a political agenda.

"It's well worth people going online to discover what they can about the allegations, about how they were made, who made them, what the people who made them did afterwards, and look at what happened."

George Galloway, the Respect MP, also caused furore by suggesting Mr Assange has been accused of no more than bad "sexual etiquette".

Mr Galloway, speaking in a 30 minute video blog on Sunday, said the allegations levelled against Mr Assange could not be considered rape.

He said: "Even taken at its worst, if the allegations made by these two women were true, 100 per cent true, and even if a camera in the room captured them, they don't constitute rape. At least not rape as anyone with any sense can possibly recognise it. And somebody has to say this.

"I mean not everybody needs to be asked prior to each insertion. Some people believe that when you go to bed with somebody, take off your clothes, and have sex with them and then fall asleep, you're already in the sex game with them.

"It might be really bad manners not to have tapped her on the shoulder and said, 'do you mind if I do it again?'. It might be really sordid and bad sexual etiquette, but whatever else it is, it is not rape or you bankrupt the term rape of all meaning."

Mr Galloway was condemned for his comments by women's rights groups, who said he was misrepresenting the law on rape.

Today he issued a statement saying he did not believe the authorities in Britain would have sanctioned a prosecution and that the allegations against Mr Assange had "all the hallmarks of a set-up".

He said: "No never means yes and non-consensual sex is rape. There's no doubt about it and that has always been my position."

But he added: "What occurred is not rape as most people understand it. And it's important to note that the two women involved did not initially claim it."

Women's groups have also been protesting this week about comments from Todd Akin, a Republican congressman, who said victims of "legitimate rape" rarely get pregnant.