March was the busiest month on record for supermarkets across Britain as shoppers rushed to stock up on vital supplies to see them through the coronavirus pandemic.

Grocery sales rose by a staggering 20.6% in the last four weeks, and 7.6% in the last 12, according to new data from Kantar, beating even Christmas shopping.

Fraser McKevitt, head of retail and consumer insight at Kantar, said: “Retailers and their staff have been on the front line as households prepare for an extended stay at home, with grocery sales amounting to £10.8 billion during the past four weeks alone – that’s even higher than levels seen at Christmas, the busiest time of year under normal circumstances.”

Although grocery sales were high in the first two weeks of March, Britons increased their shopping in the middle of the month, with 88% of households visiting a grocer between March 16 and March 19, making an average of five trips each. This meant 42 million extra shopping trips in only four days.

Shoppers have tended to focus on buying supplies more regularly, rather than massively increasing the amount they buy per trip. However, shopping trolleys have been filling up more as well.

The average household increased its spending by £62.92 over the last four weeks, with shoppers in London, where the virus hit first, spent a quarter more than they usually do.

Mr McKevitt said that shoppers will be even more dependent on supermarkets in the coming weeks, with restaurants and pubs closed across the country. This means that another 503 million meals will have to be prepared and eaten at home every week until restrictions ease.

Shoppers have also built up an extra £199 million stockpile of alcohol, a 22% rise, and spent 28% more on stock cupboard ingredients and frozen foods.

However, despite massive demand for deliveries, there has only been a minor upswing in online sales.

“Government advice may have been to get groceries delivered if possible, but limited delivery slots meant that only 14.6% of households received an online delivery in the past four weeks, up from 13.8% in March 2019 but probably well below actual demand,” Mr McKevitt said.

He added that the panic buying has been “concentrated to a relatively low number of individuals” and this will taper off as supermarkets show they are able to keep restocking their shelves.

All 10 of the main supermarkets grew in the last 12 weeks, according to the Kantar data. German discounters Lidl and Aldi performed strongly, growing by 17.6% and 11% respectively over the last 12 weeks.

At 7.4%, Sainsbury’s was the best performer of the traditional big four supermarkets. Tesco grew by 5.5%, Asda at 4.9% and Morrisons at 4.6%.

Iceland saw its sales up 11.7%, while the Co-op’s convenience stores helped boost its sales by 9.4%. Waitrose saw its fastest growth since November 2013, at 7.5%.

Online-only supermarket Ocado, which was forced to take a days-long time-out as its website struggled to cope with the traffic, attracted 133,000 new customers in the last 12 weeks, with sales growing 12.5%.