Tesco has increased its lead in the UK grocery market, while Sainsbury has also managed to improve its market share, according to the latest figures from market researchers TNS.

In the twelve weeks to 22 May, Tesco had a 29.9% share of the market according to TNS, compared with 27.6% in the same period a year earlier. Sainsbury's share rise to 15.9% from 15.5% a year ago, while Asda's fell to 16.5% from 16.6% a year ago.

TNS Superpanel communications director Edward Garner said of the Sainsbury performance that, "this represents real turnover growth of 5% and confirms the solidity of the recovery."

The combined Morrison's and Safeway share fell to 12% from 14.2% a year ago. "There are signs that this may be levelling off," Garner said. "It should be remembered that much of this decline is due to fascia changes as Safeway stores are sold off in response to the Competition Commission stipulations and, more recently, the smaller stores that have been sold to Somerfield."

Waitrose benefited from the Safeway conversions. Its market share rose from 3.2% to 3.7%, a turnover increase of 19%.