Santa Claus Conquers the Martians was written by Paul L. Jacobson and Glenville Mareth and is generally regarded as one of the worst science fiction films, indeed the worst film of any kind, ever made. But in fact it's sorely underrated - the film is fantastic entertainment. No, but seriously, it's cheap and cheerless, sickening and treacly throughout, entirely deserving its damning reputation.

It uses cardboard sets and much stock footage in the manner of a fifties sci-fi B-movie, and the special effects would shame a serial of the thirties - it's difficult to believe it was made in the mid-sixties. Such menaces as the robot and the polar bear are embarrassing to witness, and the elves in Santa's grotto look like a cross between garden gnomes and Fidel Castro.

Santa himself has a manner verging on that of a used car salesman, and a habit of breaking into maniacal laughter that becomes frankly disturbing. As the action drags on, you find yourself sympathising with the evil, heavily moustached Voldar, who piles derision on the notion of Martians having anything to do with the festive season and quite reasonably attempts to eject Santa into space.

Not even the least demanding children could find anything to laugh at here, all the jokes are poor ("Martianmallows!"), the best one being the rocket scientist named Wernher Von Green. Green - Braun - did you see what they did there? Christ. Speaking of whom, there is a noticeable lack of religion in this Yuletide. You'd think that with all those green men hanging around maybe even paganism would get a look in, but no, this is about the true spirit of Christmas - getting presents.

This film might be notable as the first to star a little (well, even smaller) Pia Zadora as a Martian girl - yes, that's the best you can say about this cinematic atrocity. Don't miss it. And then watch War of the Worlds as an tidote. Music by Milton Delugg, including the tone deaf theme song, "Hooray for Santy Claus".