Tesco has dramatically stemmed the loss of customers to cut-price “discounter” rivals such as Aldi, The Times has learnt.

According to confidential industry “switching” data, Britain's leading supermarket has also completely turned around its losses to Morrisons, the resurgent No 4 player in the sector.

Yet the figures also show that Tesco is still haemorrhaging customers to Asda, the No 2, while — for the first time in almost 18 months — it is also losing a significant amount of business to Sainsbury's.

It is understood that the data shows that Tesco has been losing sales among wealthier “AB” customers not to Sainsbury's, which traditionally has been stronger among this demographic group, but to Asda. The customer losses to Sainsbury's are thought to be more pronounced among the poorer “C2DE” shoppers.

News of the figures comes ahead of likely confirmation today that Tesco has raised its full-year pre-tax profits by 5 per cent, to just over £3 billion, despite its weakest Christmas showing in the UK for two decades. The switching data, compiled by TNS Worldpanel, the industry analysts, and based on till rolls from the supermarkets, shows that Tesco lost £5.8 million of sales to Aldi during the 12-week period to March 22. That is slightly up on the 12 weeks to mid-February, but dramatically down on the losses that Tesco was suffering to the German-owned discounter as recently as November and December last year.

This would suggest that Tesco's new cut-price Discounter range, launched last September, has staunched the flow of customers to the likes of Aldi and Lidl. The March figures also show that Tesco has started to win business back from Morrisons, to which it has been losing sales since June last year.

They also reveal that, in the latest 12-week period, Tesco lost £16.4 million of sales to Sainsbury's, reversing a trend that had seen Tesco taking sales from Sainsbury's more or less consistently since October 2007. Tesco also lost £27.8 million of sales to Asda during the period — its biggest 12-weekly loss to its American-owned rival in more than two years.

None of the supermarkets would comment on the record, but one industry source said: “Shoppers are being incredibly picky at the moment — they genuinely are shopping around and looking for deals.”

Analysts believe that the amount Tesco has invested on launching its Discounter range had prevented it from spending money on promotions elsewhere, such as on the Tesco Value ranges, than it was this time last year. It is believed this has helped Sainsbury's, in particular, which has been pushing its own Basics lines.

The Switch & Save campaign being run over recent months by Sainsbury's, highlighting how much customers can save by switching from branded goods to its own-label lines, is also thought to have contributed to recent market trends.

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