Pop superstar Lady Gaga has been sued over sales of her wristbands for Japan's earthquake relief efforts in a class action that claims that not all the proceeds went to victims as she had promised.

Michigan legal network 1800LAWFIRM also alleges that Gaga and other companies involved in the sale and marketing of the $5 white and red "We Pray for Japan" wristbands overcharged buyers on shipping costs and "artificially inflated reports of total donations".

"While we commend Lady Gaga for her philanthropic efforts, we want to ensure that claims that 'all proceeds will be donated to Japan's earthquake' are in fact true," said Alyson Oliver, an attorney for 1800LAWFIRM.

"Our intention via this lawsuit is to uncover any improprieties committed by Lady Gaga and appropriate the full donations assumed to the victims in Japan."

Lady Gaga, 25, and her representatives did not return calls for comment on Monday. The federal class action lawsuit was filed in Michigan on Friday while the "Born This Way" singer was in Japan for a benefit concert for victims of the March earthquake and tsunami.

Gaga, whose real name is Stefani Germanotta, is reported to have donated about $3 million to Japan disaster relief through sales of the wristbands and other ventures.

The official website for the singer's store however has several comments from frustrated fans complaining about long delivery times and shipping and handling costs of more than $5 for the small rubber wristbands.

The lawsuit claims that a slew of federal racketeering and consumer protection laws were broken by what it calls deceptive advertising and profits from the sale of the bracelets.

Lady Gaga was last month named the most powerful celebrity in the world by Forbes magazine, based on her earnings, media visibility and social media popularity.