Asda said it had hit a “nadir” as it reported a deepening decline in sales - with a like-for-like quarterly fall of 4.7% that was the worst in its 50-year history.

It was the fourth quarter in a row of falls for the Leeds-based supermarket, owned by US giant Walmart, and comes after sales fell 3.9% in the previous period - already the worst in more than two decades.

The figures, for the 11 weeks to June 30, come as supermarkets are struggling to see off the threat of discounters Aldi and Lidl, with official figures showing the longest stretch of food and drink price deflation on record.

Chief executive Andy Clarke said: “We have hit our nadir - our lowest point. We have got positive green shoots as we move into Q3.”

He said the sales performance had been hit by “short term tactics” by rivals. Asda has previously accused Morrisons of effectively printing money with its voucher offers.

Asda also pointed to plunging profits and balance sheet write-offs at rivals where its own bottom line had been flat and there had been no write-offs.

Mr Clarke said: “We have led the way through what has been a very challenging storm for the retail market. Although we have hit our nadir, we are on an upward curve now.”

He added that Walmart backed its strategy which includes new “save money live better” branding, avoiding short term offers as it strives to keep prices consistently lower.

Chief merchandising officer Barry Williams said it would not be involved in “trying to hoodwink or confuse our customers”.

The figures come after Asda lost its position as the UK’s second biggest grocer by market share, but Mr Clarke said it was likely to recover this soon.

“I am sure in the next couple of weeks that it will flip back the other way. We won’t make a big song and dance about it.”

He added that he was “watching carefully” over signs that online retail giant Amazon could launch its own grocery offering in the UK, but said that this was at a “very early stage”.

Asda’s like-for-like sales were 4.2% lower over the first half.

Finance director Alex Russo said: “We are going to do better than that in the second half. We are confident that this is already the bottom.”