Market researcher Kantar Worldpanel said on Tuesday Aldi's [ALDIEI.UL] sales rose 15.5 percent in the 12 weeks to Nov. 4, while Lidl's were up 10.2 percent, taking their share of the UK grocery market up to 7.6 percent and 5.5 percent respectively.

Aldi's market share growth of 0.9 percentage points was the highest year-on-year gain by any grocer in almost four years, Kantar Worldpanel said.

Unlike Britain's big four grocers - market leader Tesco, Sainsbury's, Asda and Morrisons - Aldi and Lidl are still opening new stores aggressively.

“Five years ago, just under half of British households were visiting one of the discount retailers at least once in a 12 week period. This now stands at almost two-thirds, which is reflected in their continued growth," said Fraser McKevitt, Kantar Worldpanel's head of retail and consumer insight.

Of Britain's big four Tesco, Sainsbury's and Morrisons lost share, while Asda's was flat.

Sales at No. 3 player Asda, which in April agreed a 7.3 billion pounds takeover by No. 2 Sainsbury's, rose 2.6 percent. Tesco's sales increased by 0.4 percent and sales were up 1.5 percent at Morrisons. Sainsbury's was the laggard with a 0.6 percent sales fall.

Asda is scheduled to update on third quarter trading on Thursday.

Kantar Worldpanel said overall grocery sales in Britain increased 2.6 percent, while grocery inflation was 1.8 percent. Prices are rising fastest in markets such as cola, sparkling wine and butter.

Market share and sales growth (percent)

12 wks to 12 wks to pct change

Nov 4, 2018 Nov 5, 2017 in sales

Tesco 27.5 28.1 0.4

Sainsbury's 15.8 16.3 -0.6

Asda 15.3 15.3 2.6

Morrisons 10.3 10.4 1.5

Aldi 7.6 6.7 15.5

Co-operative 6.3 6.1 5.1

Lidl 5.5 5.1 10.2

Waitrose 5.1 5.3 -1.0

Iceland 2.1 2.0 5.0

Ocado 1.1 1.1 4.3

Source: Kantar Worldpanel

($1 = 0.7757 pounds)

(Reporting by James Davey; editing by Kate Holton and Jane Merriman)