The boss of Asda, the UK's second biggest supermarket chain, turned up the heat on major rival Tesco as he pledged to step up its price guarantee scheme.

Andy Clarke said the grocer, which has more than 540 stores in Britain, has "only just scratched the surface" of the pricing strategy, which allows customers to check receipts and receive a refund if their Asda shop is not 10% cheaper than its rivals.

In a further bid to boost its sales, Asda has launched a regular study of mothers who shop at the chain, so it can further tailor its offering to its key demographic.

In its new study - dubbed the Mumdex - Asda interviewed around 4,000 mothers to gauge their views and experiences in the current economic climate and discovered some 75% had lower disposable incomes than a year ago.

Britain's supermarkets became embroiled in an intense price war since Tesco unveiled its £500m Big Price Drop last October, with Sainsbury's launching its Brand Match scheme shortly after.

But Tesco recently admitted its pricing strategy had failed after a disappointing Christmas period saw like-for-like sales excluding VAT and petrol drop 2.3% in the six weeks to January 7.

Asda was able to take market share from its number one competitor as it saw like-for-like sales, excluding VAT and petrol, grow 1% in the 14 weeks to January 7, although this was a slight slowdown on the previous quarter, when sales were up 1.3%.