Bryony Kimmings/ Shazia Mirza, Soho Theatre

At first sight there seems to be little to connect these two comics - one a performance artist who spends much of her show in her underwear, the other a self-described 34-year-old virgin - who are touring with their 2010 Edinburgh Fringe shows, except that they are both currently appearing in the same studio space at the Soho Theatre in London. But having been underwhelmed after seeing their shows back to back, I see similarities - my notes contain the common scribblings “weak material” and “overlong anecdotes” - and I'm frustrated by the realisation that both have some cracking gags among the obvious and trite stuff that forms the majority of their acts.

In Sex Idiot Bryony Kimmings tells what could be an engrossing story about retracing much of her life (she’s 29 and from boring Cambridgeshire, she tells us) to find out who gave her a sexually transmitted infection, and those whom she may have later inadvertently infected, in order to take an adult look at our sexual selves - comedy gold in the making, you may think. But whereas a comic who truly bares their soul (Kim Noble springs to mind) might take us down some uncomfortable avenues, Kimmings merely skips through some faux-revelatory cul-de-sacs with a mixture of interpretative dance, performance poetry and confessional comedy, much of it mediocre, some of it borderline embarrassing.

If it weren’t for the cleverly inserted serious message about leaving ourselves open to all sorts of risk - taking sweets from a stranger, thoughtlessly sharing bodily fluids with someone we’ve just met in the pub - and a touching mea culpa for not taking her relationships seriously, I would think it a rather decent spoof of where performing arts grads meet reality television. But it’s just not witty or insightful enough, and parts of the show - particularly a segment in which Kimmings supposedly fashions a moustache from pubic-hair clippings donated by the audience - are simply yucky.

There are one or two funny riffs, such as a catchy song composed entirely of words and phrases for the vagina - “The Road to Grimsby” is a new one on me - and a pleasing self-deprecation about her sexual prowess: “I thought I was quite a passionate lover, but most people thought I was a mental, jealous freak.” But the rich potential of the show’s title is insufficiently explored and little in this hour raises a laugh.

Shazia Mirza’s Multiple Choice has some dirty talk in it too, which is strange coming from a woman who declares early in the show that she, being a good Muslim, is a virgin. What follows is a slew of gags predicated on her being a British-Pakistani who finds herself at odds with both her strict Muslim parents and the sexually incontinent Britain she was born into: "I'm not saying all white women are slappers..."

Mirza is happy to skate the borders of taste - talking about her parents’ desperate desire for her to wed, she says, “They’ll take anything, even a ginger Jew” - but, unlike Frankie Boyle and Jimmy Carr, whose deliberately offensive comedy (whether you find it funny or not) is terrifically well written, Mirza’s is often lazy; if you’ve seen her at any time in her career, you’ll recognise large chunks of this show. Some of it is creakingly old, too: "I'm from Birmingham. I don't know why people are ashamed of saying they come from Birmingham - it looks nice now that it's finished."

Even promising subjects - Mirza says she has sexual Tourette’s, saying the wrong thing in social situations (“I’ve taken it up the arse a couple of times” to perfect strangers at parties), and thinks the British are far too PC - fizzle out. And a long riff about the time she was invited to Buckingham Palace, only to find that she was comically included in 400 prominent British-Indians (“We all look the same to them”), goes on far too long and much of it is clearly made up. Adam Hills, hardly the edgiest of comedians, has fashioned much better material out of his brief brush with the Windsors at the Royal Variety Show.

• Book tickets for Bryony Kimmings and Shazia Mirza at Soho Theatre, London W1 until 16 April
• Book tickets for Kim Noble at Soho Theatre, London W1 11-16 April
• Find Jimmy Carr on Amazon
• Find Frankie Boyle on Amazon

Watch Shazia Mirza at a Stand Up Against Racism gig