The film of the TV show opens in British cinemas this Friday, but Duchovny, 38, thinks the plots are far-fetched and "full of holes".

The actor, who plays FBI agent Mulder, told this week's Radio Times he thought the show was doomed from the start.

He said: "I assumed there was no way it would last. It wasn't that interesting and I thought it was silly. Obviously I was wrong."

Asked whether he understood the plot, he said: "Enough to know they don't make sense. There are lots of holes."

Wants to be off the show

Another "far-fetched" case for Mulder and Scully

He stands to earn $3m from the final two years of his X-Files contract, which is his only motivation for staying with the series.

He said: "I'd love to be off the TV show, but because of my greed I have to give them an extra two years."

But Duchovny thinks he's worth every cent - because without him the X-Files wouldn't have been a hit.

He said: "If I hadn't grounded its unreality in the reality of Mulder it would have become camp like Star Trek, which is not trying to be real.

"When I first read the script I realised Mulder couldn't be wild-eyed and unreliable. He's clearly insane, so he has to appear very sane to earn the audience's trust."

No friendship

He also blasted reports of frosty relations between him and co-star Gillian Anderson, who plays fellow agent Scully.

He said: "We trust each other and I am eternally grateful to her, but when the work is over she is the last person I want to see.

"People don't understand our lack of a need to have a friendship, and they think it indicates I dislike her."