The film rating 12 is to be replaced by a category that allows younger children to watch if accompanied by an adult, the censors' board announced yesterday.
The 12A category is the first change made by the British Board of Film Classification to the ratings system since 1989, when the 12 category was introduced.
The change follows repeated calls from some parents to be given the discretion to decide whether a film would be suitable for their children. The 12-rated James Bond movies have prompted the most letters from parents.
The board investigated the idea with a pilot scheme in Norwich last year, backed by research showing that 70 per cent of people supported the new rating. Robin Duval, the board's director, said that the 12A category would take effect from today.
It means that children under 12 are likely to be able to see the forthcoming 007 film, Die Another Day, starring Pierce Brosnan, and The Bourne Identity, a thriller due for release next month, starring Matt Damon.
Any film with a 12 rating already in the cinemas, including Spider-Man, will now be open to the under-12s so long as they are accompanied by an adult.
The board said that the same guidelines on content would apply to 12A films as to those rated 12. These permit scenes of brief nudity and "soft" drug-taking and the occasional use of strong language.
Films passed at 12A would be unlikely to be suitable for very young children, the board said. The change would probably apply largely to those aged 10 or 11.
Mr Duval said: "We know that the development and maturity of children varies considerably and parents know best what their children are able to deal with.''
He added: "It is important, however, that young children have an adult with them in case they are disturbed by anything they may see."