ONE in 10 shoppers claim to have started stockpiling food to prepare for a no-deal Brexit, a survey suggests.

Kantar Worldpanel noted that the claims had not been reflected in sales "just yet", with overall grocery volumes rising at a stable 1.2 per cent in the four weeks leading up to February 24.

Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel, said: "Despite one in 10 shoppers saying they have started stockpiling groceries and a further 26 per cent reporting they are considering doing so, this has not been borne out in sales just yet."

Meanwhile, Sainsbury's was the worst performer of the "big four" grocers over the 12 weeks leading up to February 24, Kantar's analysis shows.

Sainsbury's - which is trying to buy Asda for £7.3 billion - suffered a sales drop of one per cent, reducing its market share by 0.5 percentage points to 15.7 per cent.

This compared with gains of 1.3 per cent, one per cent and 0.8 per cent at market leader Tesco, Asda and Morrisons respectively.

Sainsbury's and Asda suffered a major blow last month when the competition regulator said in a provisional ruling that it could block the deal unless the pair sell off significant stores or even one of the brands.

Asda and Sainsbury's now have a potential combined market share of 31.2 per cent as they await the final Competition and Markets Authority ruling on their proposed merger.

Kantar Worldpanel said all of Britain's big four supermarket chains lost market share in the 12-week period to German-owned discounters Aldi and Lidl.

Aldi's sales were up 10 per cent, while Lidl's rose 5.4 per cent, taking their combined market share to 12.8 per cent.

Rival analysts Nielsen reported that growth in shoppers' spending slowed to 2.5 per cent in February from 3.3 per cent last month, with consumers spending less per visit as Brexit causes increased caution.

Mike Watkins, Nielsen's UK head of retailer insight, said: "Over the last four weeks, the average spend per visit has fallen to £16.30 from £16.70 this time last year, down two per cent, as a result of the resurgence of 'little and often' shopping behaviour but also due to price cutting by supermarkets."

Nielsen figures for the last 12-week period show Tesco leading with 26.8 per cent market share, followed by Sainsbury's at 14.8 per cent, Asda at 13.8 per cent and Morrisons at 9.8 per cent.

Kantar Worldpanel Plus surveyed 7,008 adults online between February 1 and 4 for its findings on shoppers stockpiling groceries.