Virgin Media, which has almost 4 million broadband customers, has signed up the world's largest music company Universal Music Group to offer its artists such as U2 and Amy Winehouse. It expects to sign up the remaining major music labels before the launch at the end of this year.
The price is expected to be between 10 to 15 pounds per month and the two firms say it is a groundbreaking world first to allow the customers to download as many tracks as they want.
But the as yet unnamed service will also inevitably compete with illegal music-downloading services, which come for free.
As part of the deal, Virgin will also have the right to temporarily suspend those customers who are repeatedly using illegal sites to download their music.