Work has begun on a Simpsons film, says the actress who gives Lisa her voice.

Yeardley Smith told reporters that writers were scribbling away, but because animation takes so long, it wouldn\'t be out for about three years.

She said: "My wish for the show is that we go out with a bang not a pimple. If we can do a movie as good as our best episodes, I\'m thrilled."

Yeardley also said that there would probably be two more series of the long running cartoon show.

Filming on the new series of the Simpsons is under threat as the actors who do many of the voices are arguing over pay.

They want to earn about ?2.3 million a year, as opposed to the ?815,000 they make now.

Fox, who make the show, are negotiating with them.