Asda’s planned £6.8 billion takeover by the billionaire Issa brothers and private equity firm TDR Capital is being investigated by the UK’s competition watchdog.

The Competition and Markets Authority (CMA) said it has formally launched its so-called phase one probe into the Asda deal after the European Commission referred the deal to the UK.

It will now look at whether the acquisition by Mohsin and Zuber Issa – the Lancashire brothers behind petrol forecourt firm EG Group, who have partnered with TDR – will lead to a “substantial lessening of competition” in the UK.

The CMA said the brothers and TDR – which have formed a takeover vehicle called Bellis Acquisition Company for the deal – requested the EC referred the deal to the CMA for review.

The CMA now has until February 18 to reach a decision on the first stage of its investigation.

It has set a deadline of December 22 for interested parties to comment.

The Issa brothers and TDR won the lengthy bid battle for Asda in October.

The deal is not expected to encounter the same competition woes as the previous ill-fated attempt by Sainsbury’s to buy out Asda, which was blocked by the CMA last year.

But it is thought the CMA may demand the Issa brothers offload some of their EG sites, having cited reduced competition in fuel retailing among its concerns when it vetoed the Sainsbury’s tie-up.

A spokesman for the Issa brothers and TDR Capital said they had expected the CMA to investigate the deal.

“We are looking forward to working constructively with the CMA to address any questions they may have,” he added.

As part of the deal, the buyers have committed to keeping Asda’s headquarters in Leeds and said they will invest to grow its convenience and online operations.

The chain’s current US owner, Walmart, will also retain a minority stake in Asda.

Blackburn-based EG Group, formerly known as Euro Garages, already runs forecourt convenience stores for Spar and French hypermarket chain Carrefour.

It has expanded rapidly from a single petrol station bought in 2001 into a global network of almost 6,000 forecourts across 10 countries and around 44,000 staff.

As well as its UK sites, it now has a presence in the Netherlands, Germany and the US.

EG Group has succeeded in attracting customers by bringing big food-to-go brands on to its sites, opening the UK’s first Starbucks drive-thru.

EG Group now operates 110 Starbucks outlets as well as the largest franchise of KFC stores in the UK, with 125 sites.

TDR Capital, which also owns the UK’s largest pub group, Stonegate, owns a 50% stake in EG Group, sharing ownership with the Issa brothers.