Britain's music and film industries launched a fight back against online piracy on Thursday, persuading the six biggest Internet providers to send warning letters to those suspected of illegal file-sharing.

Some 6 million Britons are thought to engage in illegal file-sharing each year and the trend has cost the music and film industries millions in lost revenue.

ISPs had previously argued they were mere conduits and not responsible for content. But they agreed to the deal after the British government said it would impose legislation if they did not work to curb illegal file-sharing.