What would the playwriting landscape look like if all submissions to theatres were done anonymously, removing any question of gender bias? Or at least, when plays were sent out to be considered by reading committees, the title page was removed? Some theatres already operate in that way, most notably Liverpool's Playhouse and Everyman, where readers don't know whether the author is Alan Bennett or a first-time female playwright.

I raised the question a few nights ago when I chaired a panel of women writers, directors and producers at Theatre 503 following a performance by Agent 160 , a new writer-led women's company created by Lisa Parry and others in response to the lack of plays by women. We keep being told that women are about to storm our stages and there are certainly many more than there were 20 years ago, but the female playwright with an original main-stage play in performance is still the exception rather than the rule.

The most recent research done by Sphinx theatre company shows that only 17% of produced plays are by women. A quick, slightly unscientific look at Time Out's theatre listings for London reflects this: of the 57 productions on in the West End and the fringe that might be considered plays (rather than musicals or physical work), only six are written by women. Of course that figure includes classic plays by Shakespeare and others, but the truth is that when it comes to playwriting, men have been doing it in greater numbers, and for much longer.

Birmingham Rep puts on 50% of plays by women (and brand-new plays at that) in its spring/summer season, but again it's the exception rather than the rule. If it wasn't for the fact that Shared Experience are on tour with Helen Edmundson's Mary Shelley and there are touring revivals of Sarah Kane's Crave and Vivienne Franzmann's Mogadishu, several of our major regional theatres would have no writing by women at all over the next six months. Maybe Arts Council England should have thought a little more about equality before it cut Shared Experience.

When US researcher Emily Glassberg Sands sent out identical scripts to theatres in the US in 2009, half with a male name and half with a female name, she found that those believed to have been written by women were rated significantly worse by artistic directors and literary managers than those written by men. This was even the case when many of those artistic directors and literary managers were women – suggesting that when women rise to positions of power within theatre, they don't necessarily look more positively upon women's work. There is no explantion for this but it may be that the struggle to get one of these jobs is still so hard that sisterly feelings go out of the window.

It's certainly the case that women submit fewer plays than men to theatres, but that alone cannot account for the hugely disproportionate number of plays by men. My suspicion that gender bias might be at work only increased when I took a quick look at the Bruntwood playwriting competition winners, an award in which all submissions must be entered under a pseudonym, many of which are chosen to be non-gender specific. Of the 13 prizes awarded over the last six years, five of them have been won by women – a 40/60 gender split that much more accurately reflects the number of plays submitted by women and men to theatres across the country.