The number of audio CDs being illegally copied has almost doubled in the space of a year, according to figures released by the British Phonographic Industry.

The BPI's annual report estimates the cost of illegal CDs to the industry to be more than £27m.

"Retailers, distributors and the artists all lose out when customers are sold a pirate copy rather than a legitimate recording," said the BPI.

But in 2001 CD sales in the UK increased by around five percent, dampening arguments from the industry that illegal copying was adversely affecting CD sales.

"Across the world we have seen a major slide in CD sales figures and we expect this trend to continue for some time," countered a BPI spokesperson.

People have been copying music for their own use ever since the first tape players came with recording facilities. Now, though, the industry is up against 'business orientated' copiers.

By linking several burners together, thieves can create multiple copies in minutes. The BPI estimates around 4.3 million counterfeit CD copies were created last year.

"Illegal copying has affected sales across the board. Sites like Napster gave people a window to download free music and since its closure many people are looking for new ways to find music for free," said a spokesman at record giant, BMG.

Music publishers are currently developing a number of techniques they hope will beat copiers, including special codes and blocking devices.