Some of the world's best-known atheists, including British scientist Richard Dawkins, appear in the documentary, but they are unhappy with it. They say they agreed to appear in a documentary called Crossroads, but have ended up instead in Expelled: No Intelligence Allowed.

They had expected Crossroads to be a debate about creationism versus Darwinism, but Expelled supports intelligent design (ID), a variation on creationism. The premise of Expelled is that scientists sympathetic to intelligent design are penalised by being denied academic posts.

The film, to have its premiere on February 12 in cinemas across the US, is fronted by Ben Stein, an actor and New York Times columnist. The timing may be linked to the 2008 presidential election, where creationism versus Darwinism often features in candidates' debates.

Professor Dawkins, who is speaking at the Atheist Alliance convention in Crystal City, Virginia, said in an email that had he known the film's premise he would not have agreed to take part. "At no time was I given the slightest clue that these people were a creationist front," he said. Other atheists said they were uneasy about the way they felt they had been duped.

Paul Zachary "PZ" Myers, a biology professor at the University of Minnesota and a leading critic of creationism, reproduced on Prof Dawkins' website a letter from Mark Mathis, a producer for Rampant Films. It says: "We are in production of the documentary film Crossroads: The Intersection of Science and Religion ... we are interested in asking you questions about the disconnect/controversy that exists in America between evolution, creationism and the intelligent design movement."

Professor Myers agreed to do the interview, but was surprised to see his name appear instead in what he described as "this new ID creationist movie" - Expelled.

Stein denied in the New York Times that he had misled anyone. "I don't remember a single person asking me what the movie was about," he said. The film company said the movie's title was changed on the advice of marketing experts.