Washington attorney-general Karl Racine said the company “tricked consumers into thinking they were increasing drivers’ compensation when Amazon was actually diverting tips to reduce its own labour costs and increase profits” through its Amazon Flex service.

Amazon Flex drivers use their own vehicles to deliver goods and groceries ordered through programmes like Prime Now and Amazon Fresh.

The US Federal Trade Commission (FTC) alleged the company kept drivers’ tips over a 2.5 year period and stopped the practise after learning of the FTC investigation in 2019, the FTC said in 2021.

The lawsuit, filed in the Superior Court for the district of Columbia, seeks civil penalties for every violation and a court order to bar Amazon from reengaging in the practise.

Last year under a settlement with the FTC, Amazon paid US$61.7 million to more than 140,000 drivers.

Amazon has “thus far escaped appropriate accountability, including any civil penalties, for consumer harm”, Racine said in a statement.

“When a company is caught stealing from its workers, it is not enough for the company to repay the amount stolen. Stealing from workers is theft, and significant penalties are necessary to strongly disincentivise this unlawful conduct.”

Amazon did not immediately provide a comment.

In 2021 the company disagreed that the way it reported pay to drivers was unclear.

“We added additional clarity in 2019 and are pleased to put this matter behind us,” an Amazon spokesman said at the time.