One of Sainsbury’s leading shareholders has hit out at the business for “blowing money and credibility” on its proposed merger with Asda.

The investor, who spoke anonymously to The Daily Mail, said it was no surprise that the Competition and Markets Authority (CMA) had effectively blocked the £13bn combination.

The watchdog said in its provisional findings that it had identified 629 local markets where competition could be hit as a result of the deal and suggested it would be “difficult for the companies to address the concerns it had identified”.

Sainsbury’s has vowed to try and rescue the deal, but the investor said that would be “a waste of time and money”.

According to the grocer’s latest financial figures, it had spent £17m in costs associated with the deal by September 22.

That figure is thought to have now surpassed £50m.

The shareholder told The Daily Mail: “We were sceptical of management’s confidence on the deal going through when it was announced. The CMA announcement is not a surprise, frankly.

“The tone and mood music has been negative and increasingly worse than expected as the investigation has gone on.

“The competitive landscape has got, if anything, more competitive and Sainsbury’s has now blown money and credibility on this merger.

“Sainsbury’s is vowing to fight on. This is almost certainly a waste of time and money, when management need to refocus.”

The investor urged Sainsbury’s to “cut their losses, accept the findings and walk away”.

But the supermarket giant’s boss Mike Coupe has accused the CMA of “moving the goalposts” in its investigation of the deal and could launch a judicial review of the process.

The CMA’s final verdict on the proposed merger is due to be published by April 30.