The regulator said it will look at whether the deal will impact shoppers and suppliers in the UK, including by resulting in a less competitive environment, fewer choices, higher prices, or poorer service.

It will also look at whether the deal could see the merged entity use its increased leverage to push suppliers to lower prices. However, the CMA will now look at whether the deal will result in job losses, noting that it was precluded by law from doing so.

Andrea Coscelli, the chief executive of the CMA, said: “About £190bn is spent each year on food and groceries in the UK, so it’s vital to find out if the millions of people who shop in supermarkets could lose out as a result of this deal. We will carry out a thorough investigation to find out if this merger could lead to higher prices or a worse quality of service for shoppers and will not allow it to go ahead unless any concerns we find are fully dealt with.”

Sainsbury’s and Asda have asked the CMA to move to fast-track the probe and move to the second – and more in-depth – phase directly.  The regulator said it expects to agree to the request by 31 August, unless it receives valid objections against such a move.