Aldi is widening a price gap with rivals in Britain and is still delivering underlying sales growth there, the head of its UK business told Reuters, denying the discount supermarket was suffering the effects of a fightback by bigger chains. Britain's four major supermarkets - market leader Tesco , Sainsbury's , Asda and Morrisons - have all raised their game to counter the rapid rise of Aldi and fellow German-owned discounter Lidl [LIDUK.UL], sacrificing profits to fund price cuts and improved service. All have said they have narrowed the price gap with the discounters.