Tesco, Britain's biggest supermarket chain, has revamped its price-matching scheme to give shoppers instant reductions on branded goods at the till, the latest shot to be fired in the current price war.

Tesco's existing "Price Promise" scheme gives customers a voucher to use on future visits if their basket of goods, consisting of both branded and non-branded items, could have been purchased more cheaply at its "big four" rivals - Walmart's Asda, Sainsbury's and Morrisons .

Under Tesco's new "Brand Guarantee" scheme, launched on Monday, if a customer's branded grocery shop would have been cheaper elsewhere they will automatically get the difference deducted off their bill immediately, both in-store and online.

The scheme will also price-match against promotions at Tesco's main competitors.

However, Tesco has dropped own-label goods from its price-matching scheme.

The group, which posted a more than halving in first-half profit last week, is seeking to regain market share lost to the discounters, Aldi and Lidl, with lower and simpler pricing, improved product availability and better customer service.

Chief executive Dave Lewis has signalled their will be more price cuts in the run-up to Christmas.

Last October Sainsbury's dropped Tesco from its "Brand Match" scheme, benchmarking prices only with Asda.

Earlier this month Morrisons said it will drop the price matching element of its "Match & More" card, becoming a points collection loyalty scheme.