The Competition and Markets Authority (CMA) has begun the preliminary stages of an investigation into Sainsbury’s proposed takeover of Asda.

An “invitation to comment” has been issued by the UK’s competition watchdog, inviting all those who might be affected by the takeover to voice any concerns they may have.

The information provided will determine what the CMA will investigate once it opens up its formal investigation into the takeover. All interested parties have until 4 June to submit any concerns to the CMA.

A statement issued by the CMA said: “The CMA will be considering whether the proposed merger, if carried into effect, will result in a substantial lessening of competition within any market or markets in the UK for goods or services.”

The takeover was first announced on 30 April. Sainsbury’s chief executive Mike Coupe pledged up to a 20% reduction in the prices of certain lines sold by both supermarkets, if the deal is approved. Both Sainsbury’s and Asda expect the takeover to be completed by the second half of next year.