Wake up and smell the litigation: A class action lawsuit against Apple, alleging the company new the iPod nano to be defective but sold it anyway, has been launched in the US.

The problem in focus is the widely-reported complaint that the screen scratches too easily in normal use.

The other widely-reported iPod nano complaint - that some units were prone to broken screens - has already been dealt with by the company, which promises a free replacement to affected users.

Replacement and damages demanded

Reuters reports that the lawsuit was filed in San Jose, California on Wednesday. The suit claims that the nano scratches "excessively during normal usage."

"It alleges that though Apple knew the nano had design problems, it released the product and led consumers to believe it was durable - forcing them to shoulder the cost of replacing defective music players," Reuters reports.

The fault is blamed on the polycarbonate protective film Apple places on the screen, noting that previous iPods carried thicker protective coating.

Apple - ‘deceptive and unlawful’

The full filing is available for download (as a PDF) online from the website of the lawyers handling the complaint, Hagens Berman Sobol Shapiro.

The complaint complains at: "Apple's deceptive and unlawful conduct", saying the screen scratches are a result of the company's "defectively designed product". This violates "express and implied warranties".

Reuters reports that affected consumers had to pay $25 fee to return the nano. The suit demands the return of such fees, replacement of the original iPod nano selling price and damages.

Apple has "failed to remedy the problem in any meaningful way", the complaint claims, alleging the company deleted posts on its tech-support site that discussed the problem.

"Apple declines to comment on pending litigation", company sources said.