Supermarket sales grew in April as customers spent an extra £524m on groceries compared with last year as the UK settled into life in lockdown.

Sales across the wider market grew by 9.1% in the 12 weeks to April 19 according to the latest figures from Kantar.

The data found that while people made a record-low 14 trips a month to the supermarket in April, the drop in frequency was more than offset by the highest ever recorded growth in average basket sizes.

With the majority of businesses still closed due to ongoing lockdown and social distancing measures, Kantar said the proportion of shopping trips to the supermarket made between Mondays and Thursdays increased.

As people heeded government advice to stay home, Kantar saw a marked increase in the demand for online grocery shopping. Online grocery sales now account for 10.2% of overall sales, compared with 7.4% in March.

The greatest increase in online shopping came from older and vulnerable customers, with over-65s spending 94% more on online groceries than they did 12 months ago.

While the large supermarket chains saw the significant bulk of the growth, convenience stores also enjoyed a 39% upsurge in sales for the month and now account for 16.3% of the total market spend, up from 12.4% a year ago.

In the 12 weeks to April 19, all 10 major supermarkets saw an increase in sales, with the Co-op seeing the biggest overall percentage increase of 20%, while its market share grew 6.7%.

Spending at Sainsbury’s was up 8.4% year on year, while Tesco’s spend increased by 7.2% compared with April 2019. Morrisons and Asda saw increases of 4.3% and 3.5% on the previous period respectively.

The discounters Lidl and Aldi saw sales growth increases of 14.8% and 8.8% respectively, while online specialist Ocado saw a 19.4% increase in sales compared with April 2019.

While grocery sales have exploded over the period, Kantar said that many grocers were still struggling due to the sharp downturn in demand for general merchandise and clothing and added costs associated with operating in the pandemic.

Head of retail and consumer insight at Kantar Fraser McKevitt said: “Grocery retailers and their staff have been rightly praised for keeping the nation fed and watered during the coronavirus pandemic. People are spending more time at home and eating fewer meals out of the house, which has led to a strong growth in take-home grocery sales.

“But social distancing also means that expenditure on other categories like clothes, food bought on the go and general merchandise will have been considerably lower, so for some retailers the overall picture will be more modest.”