The UK's record industry has issued illegal music downloaders with a warning that they must stop pirating music or face action in the courts.
Almost 2,000 downloaders in the US have already been sued
The British Phonographic Industry (BPI)
has said 7.4 million people in the UK are swapping songs online illegally.
"It is causing real financial damage to everyone involved in the business," said BPI chairman Peter Jamieson.
A new instant messaging campaign on the internet will be used to warn users they are obtaining music illegally.
It will tell downloaders they should disable their file-sharing software - or face court action.
The BPI has blamed a small number of "serial uploaders" for making thousands of music files available for sharing over the internet illegally.
George Michael sees his future in legal downloads
BPI chairman Peter Jamieson said there was "no excuse whatsoever" for music being taken without permission.
The UK was at the forefront of developing legal downloading technology, he added.
Other figures in the music industry are welcoming the BPI's stance against illegal song swapping.
Alison Wenham from the Association of Independent Music said: "We endorse this campaign to warn them of the action they open themselves up to."
Andy Ross, managing director of record label Boss Music said the trend for people helping themselves to music must be stopped.
"A business acquaintance has a teenage son who has downloaded 10,000 tracks and never paid for music in his life. This cannot continue," he said.
Broadcaster and music expert Paul Gambaccini pointed out flagging music sales in the US has been bolstered by legal music downloads.
Kazaa users will be greeted with this warning message
"Inexpensive paid downloads have resuscitated the US singles market, and two million sales per week are already being recorded," he said.
Music artists are also keen to embrace sharing their work via downloads - George Michael recently announced he would concentrate on releasing new material solely on the internet.
The BPI also claims this is having a knock-on effect on sales of CD albums and singles.
Downloaders' spending on albums has slid by 32% in the past year, with singles hit by 59%, the organisation said.
The BPI has said it could use two areas of the law to prosecute illegal downloaders.
The 1988 Copyright, Patents and Designs act says the music's owner has exclusive rights to its content, and it is up to them when they decide it should be made available to the public.
The move follows the latest wave of copyright lawsuits in the US, where a further 532 people were sued on Tuesday - taking the total to 1,977.