Morrisons and Sainsbury’s have increased their share of UK food sales, according to the latest data from Kantar Worldpanel.

In the 12 weeks to 4 September, Morrisons’ market share stood at 11.5%, up from 11.4% a year earlier, after its sales increased 5.3%, the fastest of the UK’s four biggest retailers.

Sainsbury’s, the UK’s third-largest food retailer, saw it sales grow 4.8% year-on-year, which meant its market share increased from 16% a year ago to 16.1%.

The Kantar data showed that the UK grocery market was growing at 4.5%, lower than food inflation, which it said was 5.3%, indicating that volumes were down.

“The grocery market continues to deliver solid growth helped by inflation,” Kantar director Martin Whittingham said. “Consumers are managing their budget by making more shopping trips but buying fewer items on each outing. These changes are at the margin but illustrate how shoppers are trying to cope with the increasing pressures on their household budget.”

Tesco and Asda saw their market share fall as their sales grew at a slower rate than the market as a whole. Tesco’s share dropped from 30.8% to 30.4% after a 3% increase in sales. Asda, owned by Wal-Mart Stores, saw its market share dip from 17.2% to 17.1% following a 4.4% rise in sales.

All four retailers are facing increasing competition from discount retailers and Aldi and LIDL both increased their share of UK food sales again.

Aldi’s sales jumped by 25.6% year-on-year, which drove its market share from 2.9% a year ago to 3.5%. Lidl, meanwhile, saw its share increase from 2.5% to 2.6% after its sales climbed 12.6%.