The U.K.'s Advertising Standards Authority, or ASA, is expected to announce a ruling ordering Amazon.com Inc. to remove claims of "unlimited one-day delivery" from its website and on other advertisements, The Times (London) reported.

The ASA has deemed Amazon's claim — that it offers next-day delivery services for all items under its Prime program — as "misleading," the newspaper reported, apparently citing a copy of the expected ruling.

The expected ruling reportedly comes after a six-month investigation into more than 200 customer complaints alleging that the company had not met its next-day delivery guarantee, according to the report.

The ASA will require the e-commerce giant to change how it markets Prime or face further regulatory action, The Times reported.

An Amazon spokesman told the newspaper that a small number of deliveries missed their promised delivery dates in 2017, citing severe weather that affected carriers across the UK.