It said that while overall UK grocery sales grew 0.5% during the 12 weeks to Sept. 8 compared to the same period last year on a value basis, households had bought 0.9% fewer items.

"As we move closer to 31 October, it seems talk about stockpiling might be just that, because we’re not seeing any evidence of it at the moment," Kantar said.

In contrast to consumers, supermarket groups have built up stocks of ambient goods, such as toilet rolls, tinned tomatoes and olive oil.

Kantar's data showed Sainsbury's recorded the smallest sales decline of Britain's big four supermarket groups in the latest 12-week period, indicating a tentative recovery after a prolonged period of underperformance.

Kantar said Sainsbury's sales fell 0.1% in the 12 weeks to Sept. 8. That compared with falls of 1.4%, 1% and 2% at market leader Tesco, Asda and Morrisons respectively.

"This was Sainsbury’s strongest period since October 2018 and it was the best performing of the big four retailers for the second month in a row," said Fraser McKevitt, head of retail and consumer insight at Kantar.

Sainsbury's had its proposed 7.3 billion pound takeover of Walmart-owned Asda blocked by Britain's competition regulator in April. It is due to update on strategy on Sept. 25 when it hosts investors at a capital markets day.

All of the big four still lost market share to German-owned discounters Aldi and Lidl, who continue to aggressively open new stores. Their combined share now stands at 14.1%.

Shares in Sainsbury's were down 2.7% at 1047 GMT, while Tesco was down 1.3% and Morrisons was down 2.7%.

Aldi said on Monday it planned to invest 1 billion pounds into Britain over the next two years despite reporting a 26% drop in operating profit for 2018.

(Reporting by James Davey, Editing by Paul Sandle and Ed Osmond)