LONDON (Reuters) - Online supermarket Ocado, discounter Lidl and upmarket food seller Marks & Spencer were Britain's fastest growing grocers over the last quarter, industry data showed on Thursday.

Market researcher NIQ said Ocado's sales rose 12.0% in the 12 weeks to April 20 year-on-year, with Lidl's sales up 9.5% and M&S's up 9.3%. All saw market share edge higher.

The data, the most up to date snapshot of UK consumer behaviour, showed market leader Tesco grew sales 5.8%, while No. 2 Sainsbury's sales were up 6.6%.

No. 3 player Asda was again the laggard, with sales falling 0.9%.

Discounter Aldi, the No. 4, saw its sales growth slow to 1.3%, while No. 5 Morrisons saw growth of 4.4%.

NIQ said in the four weeks to April 20 total till sales growth at UK supermarkets slowed to 3.4%, reflecting a slowdown in inflation, an earlier Easter and a drop in general merchandise sales.

Food inflation slowed for a twelfth month running to 3.4% from 3.7%, with products such as butter, fish and fruits falling in price.

NIQ said spending on promotions rose to 25.3% in the four week period, up from 24% in the previous month.

"Shoppers continue to shop around for the best offers. But there is a question mark about spending on fashion, technology and home goods with holidays and leisure activities more likely to see an uptick when disposable income increases," Mike Watkins, NIQ's UK head of retailer and business insight, said.

(Reporting by James Davey; Editing by Kirsten Donovan)