Britain's competition watchdog is planning a formal competition investigation into e-commerce company Amazon.com Inc, the Financial Times reported on Thursday, citing three unidentified people familiar with the situation.

The Competition and Markets Authority has been analysing Amazon's business for months, the newspaper said, adding regulator was focusing on how the online retailer uses the data it collects on its platform.

The regulator has also scrutinised how Amazon decides which merchants appear in the crucial 'buy box' - the white panel to the right-hand side of a product where buyers click to add the item to their cart, the report added.

Amazon did not immediately respond to a request for comment on Thursday.

A probe into the company may focus on whether Amazon favours merchants that also use its logistics and delivery services when deciding who has access to the buy box and to its Prime customers, the newspaper said, citing the sources.

The timing and scope of the probe were still being worked on, it said.

The investigation was likely to cover similar ground to probes under way in the European Union, according to the report.

Brussels has two open probes into Amazon - one that is looking at how the company is using data to advance its own products to the potential detriment of rivals, and another which is looking at the criteria for the use of the buy box.