Asda today claimed that it is attracting a record number of customers as frugal shoppers continue to favour cooking from scratch at home.

Britain’s second-biggest supermarket now boasts 18 million customers a week, but the announcement came as it disclosed that its sales growth in the second quarter had eased slightly to 7.2 per cent, on a like-for-like basis, compared with 8.4 per cent in the previous quarter.

Judith McKenna, Asda’s chief financial officer, said that the decline in sales was largely the result of a drop in food inflation, which she said had hit a two-year low.

Ms McKenna said: “Undoubtedly customers are more promiscuous than the were a few years ago, but they are definitely trying us for the first time and staying with us.”

The company, owned by America’s Wal-Mart, the world’s biggest retailer, said that groceries, fresh meat and frozen food were the star performers, which reflected the trend towards cooking at home and wasting less food.

Asda’s market share has reached 17 per cent, up from 16.7 per cent in the same period last year. Tesco commands 31 per cent of the market, while J Sainsbury has a 16 per cent share, according to figures from TNS, the market research group.

Industry figures show that while Asda continues to outstrip Tesco and Sainsbury’s, it is growing more slowly than Wm Morrison, Britain’s fourth-largest supermarket group.

Morrisons and Sainsbury’s have both started ambitious store-opening programmes to gain market share in parts of the country where they are under-represented.

Ms McKenna said that the prospect of increased competition by Morrisons’ and Sainsbury’s in some areas raised the importance of Asda’s online growth.

She said: “New-store growth in new markets is important for us and we continue to grow space, but it is also important to grow through home-shopping.”

Asda opened a 50,000 sq ft “internet picking” store in Morley, West Yorkshire, in July.

In the pilot store, internet orders are distributed from a dedicated store, which is not open to shoppers, instead of using shelf-pickers at normal bricks-and-mortar stores.

The store relieves the strain on nearby stores and increases the range of delivery-time options for internet shoppers.

Wal-Mart, Asda’s parent company, reported second-quarter profits of $3.4 billion (£2.1 billion), slightly down on last year, but beating Wall Street’s forecasts.

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