Troubled supermarket chain Morrisons was dealt a new blow by research showing its tie-up with Safeway was losing market share.

Morrisons recently took over the Safeway store in Haydon Wick.

The combined group saw its share of the food retail market shrink to 13.9 per cent during the 12 weeks to August 15 from 14.6 per cent a year ago, according to market research firm TNS Superpanel.

But the figures masked a contrasting picture between stores transformed to the Morrisons format and those outlets that have kept the Safeway fascia since the merger in February.

Shares in Morrisons plunged 12 per cent last month after it issued a profits warning and told of continued flagging sales at the old Safeway stores.

At the time of the update, the company described the shortfall as a "short-term hit" and said it remained confident in the business it bought for £3 billion.

Morrisons sold 19 stores to Waitrose earlier this year to ease regulatory concerns about the merger. This contributed to a 10 per cent hike in turnover at Waitrose, which also improved its market share from three per cent to 3.2 per cent.

But there was little cheer for Sainsbury's, which has two Swindon stores, which was unable to grow sales year-on-year and saw its share of the food retail market decline by 0.7 per cent.

Tesco maintained its position as the number one supermarket in the UK with 28.1 per cent of the market ahead of Asda at 16.6 per cent.