By Laura Rohde

As Napster's user numbers continue to decline, the embattled peer-to-peer file-sharing software company has issued an apology to its users for "overblocking" access to music files.

The music-swapping company has been implementing a filtering system to block copyrighted material from its users in an effort to comply with the court injunction ordered last month by U.S. District Court Judge Marilyn Hall Patel.

But in a statement posted on its Web site, Napster admitted that in implementing a range of filters to block access to songs that are copyright protected, it has unintentionally removed tracks that can legally be shared. The "overblocking" was unintentional and the company plans to refine its filters to "avoid overblocking to the extent possible," Napster said.

Napster goes on to warn its users against trying to circumvent the filters by giving the files new names. "Napster's terms of service prohibit the use of evasive measures such as pig Latin, napcameback, napsterdecoder and otherwise deliberately altering file names in order to evade Napster's filters," the company said.

While Napster continues to remain one of the most popular Web sites on the Internet, its has lost one fifth of its users since the injunction was imposed, according to a survey published Thursday by Internet analyst Jupiter Media Metrix.

Specifically, Napster's unique users fell from 15 million in February to 12 million in March, according Andreas Gutjahr, Jupiter's European marketing manager. In February, Napster was still used by 14.3 percent of online users at home in the world's 13 most wired countries, the Jupiter report revealed.