Supermarket chain Asda has been forced to change potentially misleading price deals following an investigation by the competition watchdog.

Asda was singled out by the Competition and Markets Authority (CMA) in its investigation into supermarket pricing tactics, launched following a super-complaint by Which?, the consumer rights group.

The CMA said Asda had now "given a commitment" that it would "change the way it operates 'was/now' and multi-buy deals".

The assurance means:

The Which? super-complaint was lodged in April last year, claiming retailers were creating the illusion of savings through the use of confusing pricing techniques.

That complaint has been borne out by the CMA investigation, which found there were "areas of poor practice that could confuse or mislead shoppers".

Richard Lloyd, executive director of Which?, called the CMA's investigation "a clear warning to retailers" not to mislead their customers.

"Following our super-complaint last year, we are pleased to see the CMA investigation has resulted in Asda taking action to stop misleading special offers" he said.

"Asda has been found breaking the rules and now must immediately clean up their act."

Asda chief executive Andy Clarke said: "We are consistently recognised as the UK's lowest price, full range supermarket, offering prices that are at least 10% less than those of our rivals.

"Asda has won the Grocer 33, the most credible pricing measure in our industry, for the last 18 years and we're pleased that the CMA has today recognised that we take pricing compliance seriously."