Sainsbury's has reported a fifth successive quarter of falling sales and said it expects conditions to remain challenging for the "foreseeable future".

The UK's third biggest grocery chain, which has 597 supermarkets and 707 convenience stores, posted a 1.9% decline in like-for-like sales for the 10 weeks to March 14, compared with a fall of 1.7% in the previous quarter.

The company is about to report the first drop in annual profits in a decade and chief executive Mike Coupe warned today there were no immediate signs of a let-up in the price squeeze facing the sector.

He said: "Food deflation is likely to persist for the rest of this calendar year, and competitive pressures on price will continue."

Mr Coupe pointed out that sales volumes were growing across its food business and there had been an average uplift of more than 3% on the 1,100 products where the retailer has made price reductions.

Shares opened 2% higher today as the latest sales figures were in line with City expectations.

Britain's big four grocers - Tesco, Morrisons and US-owned Asda are the other three - are engaged in fierce competition as they scramble for market share, which is being gnawed away by discounters Aldi and Lidl.

Sainsbury's will report full-year profits in May for the first time under Mr Coupe since he succeeded Justin King, who stepped down last year following a successful decade in charge of the supermarket.

They are expected to show their first fall after nine years of growth, with City analysts expecting a 17% decline to £659 million.