Shatner has won an Emmy and a Golden Globe for Boston Legal

Leonard Nimoy is reprising his role as Vulcan Spock in the film, which is due out in the US on 25 December 2008.

The film chronicles the early days of the Enterprise crew.

"I can't believe it, I'm not in the movie at all. Leonard, God bless his heart, is in, but not me," Shatner told the Associated Press news agency.

"I thought, 'what a decision to make', since it obviously is a decision not to make use of the popularity I have to ensure the movie has good box office. It didn't seem to be a wise business decision."

Since his Star Trek days, the 76-year-old actor has continued to work in film and TV and has had particular success in award-winning series the Practice and Boston Legal.

NEW STAR TREK FILM CAST Captain Kirk - Chris Pine Older Mr Spock - Leonard Nimoy Young Mr Spock - Zachary Quinto Scotty - Simon Pegg Nero - Eric Bana Uhura - Zoe Saldana Chekov - Anton Yelchin Sulu - John Cho Leonard 'Bones' McCoy - Karl Urban

Director JJ Abrams announced last summer that Nimoy, 76, would come back as Spock, made famous with his crew mates by the 1960s television show and six Star Trek films.

The director also said Shatner would probably have a part in the film.

But Shatner said he had had a couple of meetings with Abrams, creator of Lost, without anything coming of them.

Little-known actor Chris Pine has been chosen to play the young Captain Kirk in the new film.

Heroes star Zachary Quinto will play the young Spock and Lord of the Rings actor Karl Urban will play Leonard "Bones" McCoy, the Starship Enterprise's medical officer.

The movie will show the crew meeting at the Starfleet Academy and embarking on their first mission.

The Paramount Pictures film is expected to begin shooting in November.

The Abrams film will be Star Trek's 11th big screen outing. The most recent Trek film, Star Trek: Nemesis, was released in 2003.