London (CNN Business) Amazon's play for the UK food delivery market is in doubt after Britain's competition regulator said the company's planned investment in Deliveroo could harm customers.

The Competition and Markets Authority said in a statement Wednesday that the deal could reduce competition for online deliveries of restaurant meals and groceries.

"There's a real risk that it could leave customers, restaurants and grocers facing higher prices and lower quality services as these markets develop," Andrea Gomes da Silva, the regulator's executive director, said in a statement.

"This is because the significant competition which could otherwise exist between Amazon and Deliveroo would be reduced," she added.

gave Amazon and Deliveroo five working days to submit proposals addressing its concerns. It will then decide whether to refer the case for an in-depth investigation, which could hamstring Deliveroo in the Just Eat JSTTY Uber UBER The antitrust authoritygave Amazon and Deliveroo five working days to submit proposals addressing its concerns. It will then decide whether to refer the case for an in-depth investigation, which could hamstring Deliveroo in the ultracompetitive UK market and give rivals andEats a boost.

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