Britain's Virgin Media has sent a round of warning letters to 800 of its customers whose ISP accounts have been used for illegal file-sharing.

It's the first salvo in a groundbreaking new "education" campaign agreed between Virgin Media and labels body the BPI, the end-goal of which is to enable the media group's broadband customers to legitimately download music on its network.

Through the initiative, announced in early June, Virgin Media customers who have been found to distribute music files in breach of copyright will receive informative letters, one from each party.

User accounts are identified to Virgin Media on the basis of information supplied by the BPI.

The letter issued by the BPI begins, "We're writing to you about enjoying music on the internet and about illegal downloading and filesharing. It's an issue which affects you, so it's very important that you read this letter carefully." The notice is signed-off by Geoff Taylor, CEO of the BPI.

The letters arrive in an envelope marked: "Important. If you don't read this, your broadband could be disconnected."

Virgin Media's collaboration with the BPI demonstrates something of a new dawn in relations between ISPs and copyright owners in the U.K.

Following a volley of criticism from within the music industry, ISPs have come under government pressure to find a voluntary solution on filesharing, or face legislation from early 2009.

Since the breakthrough between the BPI and Virgin, leading British broadband service provider BT has begun issuing notices to its subscribers warning it will disconnect them from the Net should they illegally share copyright-protected music on its networks.

According to the BPI, more than 6.5 million consumer broadband accounts in the U.K. are used to access music without permission using peer-to-peer services.