"You can't do jokes about black people or Asian people," the Australian comic Jim Jeffries told me last year, "but you can do a rape joke onstage now and there's not a problem." Interviewing several comedians for an article about offensiveness in comedy, I heard the same story time and again. American standup Scott Capurro told me that "talk about raping women [is] like the new black on the comedy circuit". Edinburgh comedy award-winner Brendon Burns talked about comedy's favourite neologism "rapey", meaning sleazy. "Only Britain," said Burns (another Aussie), "could make rape sound twee."

Examples of rape comedy are easy to find. Reginald D Hunter has a routine that begins, "civilisation couldn't have arisen without rape . . ." Jimmy Carr, of course, has several one-liners on the subject ("What do nine out of 10 people enjoy? / Gang rape."). In a characteristic play on his words, Carr has called his current show Rapier Wit.

When the Andrew Sachs controversy was still a twinkle in Jonathan Ross's eye, Russell Brand caused an outcry in Northampton when he prank-called the police live onstage claiming to have spotted a man wanted in the city for serious sex attacks. Even the women are at it: Geordie comic Sarah Millican has a skit about fetishistic rape roleplays with her boyfriend.

Various defences are cited for this new comedic fashion. It is comedy's job, say some, to probe the boundaries of the sayable, and to breach taboos – although some taboos are easier breached than others. It is taken as read, say others, that no harm is meant by these jokes; that they are funny precisely because everyone present – performers and audience – instinctively senses that rape is a shocking thing.

Some comics argue that rape jokes are justified as long as the joke's on them. Jeffries talked to me about his joke "about a girl who won't have sex with me . . . And the punchline is 'so I raped her'. But," he added, "I also have a joke later on about being in the toilet of a gay bar, and the punchline of that joke is 'so he raped me'. I throw it back and forth."

The counter-argument, expressed most forcibly by Jo Brand, is that today's comedians pose as plain-speakers and PC refuseniks in order to smuggle in the kind of misogynist comedy last seen in the 1970s. The likes of Carr, says Brand, "appeal to all the people out there who think, 'Where have all those delicious anti-women jokes gone? We miss them.'" Brand identifies "almost a desperation to make [comedy] more unpalatable than it was before".

But what's striking is how palatable the rape joke in comedy now appears to be. The young sketch troupe Late Night Gimp Fight were entirely unapologetic about their scene at Edinburgh last month, in which Sleeping Beauty wasn't kissed awake by her prince, but raped instead. Jeffries maintains this kind of thing is "not a problem". But, as rape becomes ever more commonplace a subject for comedy, it no longer seems terribly funny either.