THE supermarket giants' battle for top place in the nation's hearts and pockets moved up a gear after new figures revealed good news for Asda.

The Leeds-based chain has overtaken arch-rival Sainsbury to become Britain's second biggest grocer.

Asda said figures from independent retail analyst Taylor Nelson Sofres showed that, on the basis of packs sold, the supermarket chain had 15.4 per cent of the grocery market, compared with Sainsbury's 15 per cent.

However the figures covering the 12 weeks to December 10, were disputed by Sainsbury's which argued that using a volume measure - or goods actually sold - as Asda had done was not the best calculation of market share.

It pointed to Taylor Nelson Sofres' analysis based on till roll share - or the value of goods sold at the checkout - that showed Sainsbury's was still in second place.

This showed, in the 12-week period, Sainsbury's had a market share of 11.9 per cent against Asda's 11.2 per cent.

Sara Weller, Sainsbury's director of marketing, said: ''All the accepted methods of calculating market share continue to show Sainsbury's as the number two.

''As usual, Asda is being very selective in the data it has chosen to use in yet another attempt to mislead consumers.''

The two still have some way to go to catch up with market leader Tesco, which has a market share of 23 per cent.

Safeway, which was recently promoted to the FTSE-100 Index of leading stocks, still comes in fourth, on 9.7 per cent.

Asda chief operating officer Paul Mason said the increase was down to the chain's strategy of reducing prices and improving services.

Asda has been gradually closing the gap on Sainsbury's. Five years ago it was 6.1 per cent behind Sainsbury's, but last year was just 1.4 per cent behind.

The news will come as a further blow to Sainsbury's, which has been struggling to turn around its business ever since being overtaken by Tesco for the number one slot in 1996.

In early trading on the London Stock Exchange today, Sainsbury's shares were unaffected by the news and stood at 405p.