'N Sync's CD has also used protection technology

Another complained that the CD would not play on computers running the Linux operating system.

Record company BMG has admitted it is "concerned" about the complaints but says that complaints have only been received from about one customer for every 1,000 CDs shipped to shops.

The company said that the exercise was a "test" but added that BMG would continue to pursue the use of technologies which would prevent CD copying.

"The testing phase is proceeding in a way that we want to pursue it," said BMG spokeswoman Regine Hofmann.

Imbruglia's CD contains technology called Cactus Data Shield, developed by Tel Aviv-based company Midbar.

Similar CD copy protection was also included on 10,000 CDs released by Sony in the Czech Republic and Slovakia last year.

Alarm

Sony has also been testing the technology on the last album from boy band 'N Sync.

Sony, BMG and the other major record companies - Universal, Warner and EMI - are all keen to employ technologies that will limit the digital duplication of CDs.

But some consumers are alarmed, and say that record retailers are not making the distinction between normal and copy-protected CDs clear enough.

In September a California woman sued a record company and technology firm after she found out her new Charley Pride CD contained a copy protection scheme that prevented it from being played in her PC.

Karen DeLise's attorney has said she is not seeking damages, but would like better information on the packaging about what CDs will and will not do.