Kenneth Branagh is one of the 100 signatories
Some of the biggest names in film and TV have called on the government to prevent internet piracy.
Kenneth Branagh and Richard Curtis are among the directors and producers who have signed a letter demanding action be taken on illegal file sharing.
Published in the Times, the letter says TV and film-makers are "very concerned" that their work is being "undermined".
They want the government to force internet providers to stop customers from downloading films and TV shows.
"We are very concerned that the successes of the creative industries in the UK are being undermined by the illegal online file-sharing of film and TV content," the group of more than 100 signatories said.
"At a time when so many jobs are being lost in the wider economy, it is especially important that this issue be taken seriously by the government and that it devotes the resources necessary to enforce the law."
It adds that if internet service providers "are not prepared to act responsibly, they should be compelled to do so".
The likes of Billy Elliot director Stephen Daldry, The Fast Show writer Charlie Higson and writer Lynda La Plante are all supporting the campaign which is being backed by Bafta and the UK Film Council.
James Bond star Daniel Craig fronted an advert to support the campaign
Callum MacDougall, executive producer on the latest James Bond film Quantum of Solace, said file sharers were effectively "stealing from producers and distribution companies".
"If ISPs are not forced to put a stop to it, there will be no product to download because if the industry isn't recouping its costs it will stop producing," he told Radio Five Live.
"They have to enforce with their customers what the law is - if people are putting illegal downloads on their site they have to stop making them accessible," he said.
MacDougall said the worst offenders were file sharers in Africa, South America, India and the Far East, although he said the impact to the creative industries in the UK would be "untold" if action was not taken.
He added the industry lost £500m in illegal downloads last year.
Becky Hogge, executive director of digital rights campaign body Open Rights Group, said: "The Open Rights Group does not condone illicit file sharing, but pushing the problem onto internet service providers is not going to make it go away.
"The creative industries need to play their part too, by making content available in ways consumers in the digital age want to watch it.
"Illicit file sharing is a business-model problem as much as it is a law enforcement one."