The BPI blames downloading for a fall in UK single sales

The British Phonographic Industry (BPI) will announce its first legal actions on Thursday, having monitored unofficial sites where music is shared.

It says people should be using legal download sites and blames "music piracy" for falling sales of singles.

BBC correspondent Rory Cellan-Jones said critics would ask whether firms should be suing their customers.

'Major uploaders' warned

The moves in Britain follow court action in the US against hundreds of people, aged from a 12-year-old girl to a 66-year-old grandmother.

The BPI warned in March that it would take legal action and sent thousands of internet messages warning "major uploaders" they were being watched.

But it says some are still putting their whole music collection on the web illegally for other people to share.

Legal action will be aimed at the 15% of people it says are responsible for 75% of all illegal internet file-sharing.

The BPI says single sales have more than halved in the UK since 1999, when downloading took off - despite research suggesting it has a minimal effect on sales.