Aldi has hit a record market share of 5%, according to the latest grocery market share data from Kantar Worldpanel.

Its market share grew to 5% in the 12 weeks to 1 March, versus 4.3% a year ago, Kantar said. It also chalked up sales growth of 19.3%.

Tesco, meanwhile, notched up its best performance in 18 months with sales growth of 1.1%, though its market share slipped from 28.8% a year ago to 28.7%.

It was the only one of the big four to post an increase in sales. Asda saw it sales fall 2.1% during the 12-week period, while Sainsbury’s fell 0.5% and Morrisons by 0.4%. All three retailers also saw their market share decline, to 17%, 16.8% and 11% respectively.

In contrast, Waitrose posted sales growth of 4.9% and grew its market share from 5% to 5.2%. Lidl notched up sales growth of 13.6%.

It was tougher for The Co-operative, however, which saw its sales fall 2.1%, while Iceland’s sales fell 0.5%.

“Among the big four supermarkets Tesco has been the standout retailer,” said Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel.

“It has posted its strongest performance in 18 months with sales up 1.1% compared with a difficult 2014. Increasing sales have helped Tesco arrest its falling market share, which is down just 0.1 percentage point compared with last year.”

Meanwhile, Kantar also said deflation had reached a new low of -1.6%.

“A combination of lower general inflation and the grocery price war has saved shoppers £400 million in the past 12 weeks,” McKevitt added.

“All of the major supermarkets are cutting prices to win shoppers, especially within everyday staples such as eggs, vegetables and milk. Retailers are focusing their efforts on simple price cuts rather than complicated multibuy deals.”