LONDON: Britain''s biggest Internet providers have signed an agreement with the country''s recording industry to clamp down on illegal downloading, in a move announced by the government Thursday.

Under the deal to get tough on the estimated 6.5 million Britons who have downloaded music and video illegally, letters will be sent to the most prolific offenders warning them that they have been detected.

The British music industry could lose up to one billion pounds (two billion dollars, 1.27 billion euros) in lost revenue over the next five years from illegal downloading via file-sharing sites, according to estimates.