UPDATE 1-Britain agrees plan to tackle online music piracy

(Adds reaction, details)

By Kate Holton

LONDON, July 24 (Reuters) - 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.

Analysts said the plan would likely scare off younger users of illegal sites, who download content often without their parent's knowledge, but would need to be just the first step in an escalating battle.

"You could quite easily wipe off a million people from illegal file sharing sites in the UK, and if that is achieved, then that would be one of the largest single successes ever against file sharing," Jupiter analyst Mark Mulligan told Reuters.

"But that will not be enough."

The plan follows moves by France to engage Internet service providers in tackling copyright infringement on their networks and as countries such as Australia, Denmark, Japan and New Zealand launch similar discussions.