When it comes to sex and censorship, Government's insistence that laws are "evidence-based" is little more than hot air.

The statistics quoted in support of any given case are frequently misleading, partial, and - according to one expert in this field - subject to highly unethical collusion of interest between government and researchers.

From rape to lap-dancing, from internet harm to obscure sexual practices, "evidence" is used to back a narrow politicised agenda, rather than as a basis from which to develop policy.

A good – or bad example – of this approach can be found in the Lilith Report on Lap-dancing, produced in 2003, which sought to link sex crime in Camden with the opening of local lap-dancing clubs.

Sponsored by Eaves Housing For Women – of whom more later - the report quoted, without full context, some selected figures: over a three-year period, the level of sexual offences in Camden fell by less than in two allegedly comparable boroughs, and the level of recorded rape and indecent assault in Camden increased by 50 and 57 per cent following the establishment of two mainstream lap-dancing establishments.

As "research" goes, this contains more holes than the proverbial Swiss cheese. We asked the Eaves Project for comment, but at time of writing had not received an answer.

It is an absurdly simplistic "correlation equals effect" argument, with virtually no controls of any kind. Yet such is the political desire that this report be true, it is quoted frequently and as gospel – from the Guardian to Amnesty’s official site - whenever a journalist wishes to take a pop at lap-dancing.

But then, it was ever thus. The first and ground-breaking research into sexual behaviour was the 1948 Kinsey report in the United States, followed by Mass Observation’s "Little Kinsey", whose findings – including a high level of homosexual experimentation and marital infidelity - were considered so shocking that they were, in typical UK fashion, kept secret for decades after.

Kinsey came in for serious academic criticism on the grounds of sample selection (volunteers who came forward for interview were mainly self-selected) and sample bias (a high proportion of prison inmates and prostitutes). This in turn led critics to argue that both Kinsey’s focus and findings were coloured by his own interest in masochistic and promiscuous sex.

However, a subsequent re-working of Kinsey’s data suggested that the sample bias had little effect and that in general, people’s sex lives were more colourful and more varied than conventional moralists liked to imagine.