Supermarket sales soared faster in the past three months than at any point in at least 26 years, as the extent of shoppers stockpiling became clear, according to new data.

And with improving weather, more shoppers headed to parks and castles for picnics as sales of chilled dips, crisps and fizzy drinks all jumped in the past four weeks, researchers at Kantar said.

The VE Day bank holiday on Friday May 8 also helped make the preceding Thursday the biggest shopping day of the month with £488 million spent on groceries. Ice cream and alcohol sales were 40% and 50% higher than last year respectively.

Shoppers are tentatively returning to supermarkets, although the lack of hungry workers in offices and school closures is offsetting some of the growth, it added.

Kantar found that sales jumped 14.3% in the 12 weeks to May 17 in grocers, including the period of lockdown when restaurants, bars and pubs shut their doors to customers.

Online shopping hit a new peak – accounting for 11.5% of all grocery sales after the Government encouraged families to turn to home deliveries.

And in more recent weeks, customers are heading back into stores but sticking with bigger weekly shops – a trend Tesco boss Dave Lewis had already revealed he has seen.

Fraser McKevitt, head of retail and consumer insight at Kantar, said: “People have been working their way through their store cupboards over the past couple of months and some will now be spending a bit more on each visit to the supermarket to replenish supplies.”

He added: “While these are bumper figures, it remains true that the overall picture for some grocers will be less positive, as supermarkets continue to feel the impact of a considerable reduction in on-the-go spend on meals, drinks and snacks.

“Those categories usually add up to £1 billion over the course of 12 weeks and they aren’t included in these numbers.”

He also explained that with shoppers visiting supermarkets 3.5 times a week on average, 100 million fewer trips were made – although spends per trip increased 50% to £27.41 on average.

Families with adult children have seen the greatest increase in spending, with an average monthly spend of £618 versus £545 last May.

Online shopping gained more ground, adding more shoppers in 2020 than at any point in the previous five years and takeaway deliveries are up 250% year on year.

Mr McKevitt added: “While the gains made by online shopping are unlikely to be sustained at these levels, the crisis has certainly accelerated the move towards online.

“The grocers have attracted a new group of customers, in particular older demographics, and we expect some of them may continue using online services and enjoying the convenience that home delivery provides.”