Worldwide sales of legally downloaded music tripled to $1 billion last year, according to a report released today by the industry's leading trade body.

But despite 20,000 court actions launched against individuals across the world in 2005, the level of illegal file-sharing remained unchanged.

The International Federation of Phonographic Industry estimates that there are currently 885 million copyrighted music files available on the internet for illegal download.

By comparison, the number of tracks legally available doubled to over two million songs. In total, music fans downloaded 420 million tracks legally last year.

The IFPI warns that the growth in legal sales is powered by new downloaders, not by existing illegal filesharers switching to legal services. It has vowed to lead efforts to contain online piracy.

A wave of court rulings last year gave the recording industry its most significant boost yet in the fight. Judgments against Grokster in the US and Kazaa in Australia made clear that the operators of peer-to-peer networks who encourage the use of their networks for copyright infringement can be held liable for music piracy.

Meanwhile, legal sales were fuelled by the rapid growth of online music stores and the increasing popularity of downloadable mobile phone ringtones.

The Digital Music Report says music is driving digital commerce worldwide. Last year global consumers bought over 60 million portable digital mobile players, worth an estimated $9bn.

The IFPI say shifting pirates to legal services is a long-term challenge. According to the report, 6 per cent of internet users regularly download legally in the UK and Germany, compared to 5 per cent who swap files illegally.

"The challenges we now face are far too big for any complacency," said IFPI chairman John Kennedy. "In particular we need more cooperation from service providers and music distributors, to help protect intellectual property and contain piracy."

The report says that legal downloaders are more likely to be starting from scratch than migrating from illegal websites, and only one in five legal music downloaders is also an illegal file-swapper.

Changing attitudes is a key part of the music industry's strategy. The latest IFPI consumer survey, conducted by Jupiter Research, shows that a combination of education and deterrence can change consumer attitudes. The survey of 4,000 consumers across Europe showed that 35 per cent of illegal file-sharers have cut back or stopped the activity, while only 14 per cent have increased.

Last year was outstanding for digital music in the UK. James Blunt topped the first ever European digital download chart and Sheffield-rockers Arctic Monkeys promoted digital versions of their music online before releasing any tracks offline.

When the Arctic Monkey's released their debut single I Bet You Look Good On The Dancefloor in November, it went straight to No 1. The band's second single When The Sun Goes Down is predicted to reach the top spot this weekend.

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