Retail giant Amazon has begun selling chilled and frozen food products online amid speculation it is to launch a full-scale assault on the grocery market.

The US-owned firm from today began offering a range of 50-60 products to customers in London and Birmingham using its ultra-fast Prime Now service which allows items to be ordered for delivery within 60 minutes.

Among the products are low fat butter, Cathedral City cheddar, Chicago Town pizzas, Ben & Jerry ice creams and Bird’s Eye fish fingers. They are among 10,000 products offered on the Prime Now service.

Amazon said: “Prime Now customers already benefit from ultra-fast delivery on everything from essentials like bottled water, coffee and nappies to must-have products like the latest video games and devices.

“We are excited to be adding a range of chilled and frozen items to this selection as we continue to expand the number and variety of products that can be ordered for delivery within 60 minutes.”

But a spokesman declined to comment on a report in trade publication Retail Week that it was gearing up for a full grocery launch early next year.

A roll-out of a new online delivery service by one of the biggest retailers in the world could be seen as a new threat to the big four supermarkets Tesco, Sainsbury’s, Asda and Morrisons – already under pressure from discounters Aldi and Lidl.

There has already been speculation about such a move after it leased a former Tesco warehouse in Surrey.

Amazon came to prominence as an online bookseller before moving into a much wider range of products and even making TV programmes.

It launched its Amazon Fresh food operation in the US in 2007 and analysts have long speculated about a move to try to grab a slice of the UK grocery market.

There has been anger over the retailer’s tax affairs. In May it emerged that the UK arm of the business paid just £11.9 million in tax last year, despite taking £5.3 billion in sales from British shoppers.

It recently faced criticism over alleged poor treatment of workers in a New York Times expose, though boss Jeff Bezos reportedly told staff in an internal email: “I don’t recognise this Amazon and I very much hope you don’t either.”

Amazon employs more than 7,000 staff in the UK.