Pirate copies of blockbuster hit The Matrix Reloaded were available to download online, less than two weeks after the film went on release around the world, BBC News Online has learned.
A high-quality copy of the film was being downloaded by hundreds of people each day via a website which uses the file-sharing computer program BitTorrent.
The website was subsequently taken down on Tuesday.
The availability of the film online will come as a blow to executives who co-ordinated a worldwide release of the film in an attempt to thwart piracy.
Low-quality copies of the film on DVD have also been reported for sale at a major traders' market in London.
Although it is not unusual for pirate copies of blockbuster films to appear on the internet soon after release, they are often of poor quality, filmed on a hidden videcamera by a cinemagoer.
The picture is often jerky, with poor sound, punctuated by ambient noise in the cinema.
But the copy available using BitTorrent appeared to be have made from a film print, and was in widescreen format with surround sound.
A computer user with broadband internet access could download the film in about three hours.
The download also includes a teaser trailer for the third film in the sci-fi trilogy, The Matrix Revolutions.