Virgin Media and the British Phonographic Institute (BPI) are to send warning letters to customers they believe are downloading or distributing music illegally.
The announcement represents the first such public deal between the BPI and an ISP.
The pair hope that the new campaign will avoid users risking disconnection and possible legal action.
"Virgin Media's fibre optic broadband is a great platform for people who want to download lots of music," said Virgin Media in a statement.
"But we want them to do so without infringing the rights of musicians and music companies."
Customers whose accounts appear to have been used to distribute music in breach of copyright will receive "informative letters" from Virgin Media and the BPI.
Both letters will be sent by Virgin Media and the BPI will not be given customer information.
The BPI believes that many customers are not aware that their account is being used in this way, particularly in the case of parents whose children are indulging in unlawful file sharing.
"Education is absolutely key to reducing the extent of illegal downloading, and we are pleased to be working with Virgin Media on this campaign," said Geoff Taylor, chief executive of the BPI.
"We believe that new partnerships with ISPs can help build an internet in which music is properly valued.
"This will benefit not just musicians, songwriters and labels, but all internet users who love music. This joint campaign is the first step towards achieving that goal."
The BPI hopes that repeat offenders who have been given several warnings will have their accounts disconnected, followed by possible legal action.
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