May 16 (Reuters) - Consumers filed a lawsuit on Friday against Amazon.com Inc. seeking reimbursement for costs they were charged in the form of price increases as a result of tariffs that the U.S. Supreme Court later ruled President Donald Trump had imposed illegally.

Consumers said in a proposed class-action lawsuit filed in federal court in Seattle that the e-commerce giant collected hundreds of millions of dollars in illegal tariff costs by raising prices on imported goods before the Supreme Court issued its ruling.

The Supreme Court had concluded in February, in a decision issued by a majority of six to three, that Trump had exceeded his authority by using the International Emergency Economic Powers Act to impose his sweeping tariffs.

Thousands of companies began demanding billions of dollars back from the government following the ruling.

But Amazon did not do so, which the lawsuit alleged was "not because it lacked the legal basis to do so, but because it sought to curry favor with Trump by allowing the federal government to hold the funds."

The lawsuit stated, "The problem is that the money Amazon uses to stay in the president's favor does not belong to Amazon... This money was illegally taken from consumers to cover fees that were subsequently revoked."

The lawsuit emphasizes allegations of illicit enrichment and violation of Washington State Consumer Protection Act.

Amazon did not respond to a request for comment.

The lawsuit follows several previous cases filed by consumers accusing companies including Costco, Nike and FedEx of failing to return customs duty refunds to consumers.