Director Mike Leigh has quietly become a national treasure, by virtue of his relentless pursuit of truthful performances in a string of eclectic dramas, comedies and period pieces. Some are all three. On television he made his name with hits such as Abigail's Party and Nuts In May, while his film career features such celebrated work as Naked, Secrets & Lies and the Gilbert & Sullivan biopic Topsy-Turvy. Vera Drake, a drama revolving around a back-street abortionist, may yet surpass them all.

Vera Drake is set in 1950, but its issues are still relevant aren't they?

I think it is as much an issue for today as any other time. As far as we were concerned, we were dealing with a universal issue. Even though it's true that someone who needs it can get an abortion, that doesn't diminish the pain of the whole thing. There is a moral dilemma involved and what I've tried to do with the film is to confront the audience with that moral dilemma in a subtle and gentle way, rather than bludgeon anybody around the head with it.

Did it surprise you that one of the first successes you had was in a staunchly Catholic country at the Venice Film Festival?

When we showed it at Venice, Vatican radio was actually quite supportive of the film. And there were two pieces in the Catholic Herald, which talked about it in a very open and quite supportive way given the nature of things. Obviously, some people will find it objectionable, although the interesting thing is that it works because it's not dealing in black and white polemics. It draws you into feeling about things, thinking about them. That's why I think it does embrace different factions.

Your father was a doctor. Did that have any direct relevance to your doing this film?

I would have loved to have talked to my Dad, who was a GP in a very working class practice in Salford, when we were doing the film. There's no doubt he would have certainly had to deal with people who wanted to terminate their pregnancies and, certainly, the aftermath of abortions that had gone wrong. I would doubt that he performed abortions himself - I actually don't know that - but I would have seriously doubted it. But he died nearly 20 years ago. And while my mother was a midwife, again I didn't really talk to her about these things. The film doesn't come from any direct experience in that respect, Dad certainly didn't come home at tea-time and talk about it.

The moment when Vera is confronted by the police comes as a shock in the film. Given the very particular way that you work, was there a moment in the rehearsal process when it came as a similar shock to Imelda and her co-stars?

It's a standard procedure with making these films that nobody knows anything other than what his or her character would know at that stage. So when we reached that point in the rehearsals that actually all happened. The other actors didn't know she was an abortionist. And indeed Imelda didn't know the cops were about to come in, she didn't even know that there were actors playing police. So it was a quite nail-biting and fantastic seven or eight hour improvisation.

When you are recreating a very specific period like this do your own memories get triggered by the looks or sounds evoked in those scenes?

There are moments. I came from a family where nearly everyone wore specs and everyone smoked in that way, so that look was very evocative. There's one character, Lily, who reminds me in a half-conscious, subliminal way of all kinds of grown-ups I knew when I was five, six or seven. So yes, that does happen.