The film is considered a sci-fi classic

The advert for the director's cut of the film featured one scene in which the alien creature leaps and attaches itself to an astronaut's helmet.

Three viewers complained about the pre-watershed ad on Channel 4, saying it was too frightening for children.

The Independent Television Commission agreed it should only have been shown after 2100. Channel 4 apologised.

Viewers complained after seeing the advert at about 1800 GMT on 26 October last year during a break in the programme Scrapheap Challenge.

One viewer said her children aged two and four were upset by the ad, which showed shots of the characters looking terrified and screaming.

The trailer ended with a close-up of the alien's face accompanied by a woman's piercing scream.

The ITC said the advert had been approved by the Broadcast Advertising Clearance Centre (BACC) for post-watershed viewing, but had been shown in error by Channel 4 and other networks.

It called on them to tighten procedures to make sure there was no repeat of the mistake.