The internet entrepreneur credited with the dubious honour of all but inventing online piracy has revealed he is to launch a fresh attempt to bring free music to millions of US web users.

Sean Parker, now best-known for contributing to Facebook's success, incurred the wrath of the world's biggest record labels a decade ago when he co-founded Napster, a site which allowed users to share their music libraries over the internet for free. He was forced to shut it down in 2001 amid a barrage of legal suits.

But the charismatic venture capitalist has announced he is to begin another foray into the music industry after buying a £9.3m ($19.5m) stake in Spotify, a London-based site that allows listeners to enjoy free music streamed over their computer, in exchange for tolerating the odd advertisement. Users can also opt for paid service without ads.

Mr Parker, whose profile skyrocketed after he was portrayed by Justin Timberlake in a film about Facebook's success, The Social Network, revealed he thought bringing Spotify to America would make up for the failure of his previous effort to crack the market.

"With Spotify, I want to finish what I started with Napster," he said. His multi-million dollar investment has bought him five per cent of the business. However, the 30-year-old's attempts to relaunch Spotify across the pond are again being hampered by a lack of cooperation from the US music industry, which is not keen on the European company's free music model. They are believed to prefer a system which would give listeners a free sample, before forcing them to pay for further access.

The strength of iTunes, the online music store owned by Apple, is also said to be causing problems. Record labels only earn very small sums from each track sold on the service, meaning they are reluctant to give away rights to their catalogues too cheaply to another online operation.

Spotify's US launch has already been postponed twice because of delays in securing deals with the major labels. Talks with EMI, Sony, Universal, and Warner are ongoing. Mr Parker has said he hopes it could get the go-ahead by the end of the year, but some industry analysts remain doubtful.

The site has been a runaway success in Europe, with around seven million users and 500,000 paying customers. However, similar attempts to allow users to listen to streamed music online have flopped in the US.

Mr Parker, who first learned basic programming at the age of seven, is also keen to encourage Spotify users to buy a version of the service for their iPods and smartphones. "Consumers are willing to pay for convenience and access," he said. "We've got you by the balls."

The site is already able to integrate with Facebook, Mr Parker's former firm. The feature allows listeners to share their favourite tracks and bands with friends.

Controversy has never been far from Mr Parker, who was sentenced to community service for hacking at the age of 16. He then left Facebook under a cloud after being arrested for cocaine possession. He was never charged.

Earlier this month, he also dipped his toe into the world of politics, donating $100,000 to a campaign to legalise cannabis in California. He has not yet commented on the gift towards the "Yes to Proposition 19" cause, also known as the Regulate, Control and Tax Cannabis Act, 2010. Californians will vote on the issue on 2 November as they head to the polls for America's midterm elections.