Tesco's customers are defecting to its rivals Asda and Wm Morrison at record rates, The Times has learnt.

Previously unpublished “switching” data provided by the industry analysts TNS Worldpanel reveals that, in the 12 weeks to November 2, about £22 million of spending was switched directly from Tesco to Asda.

Just over £10 million more went from Tesco to Aldi, the German-owned discount retailer, in the period and almost as much again to Morrisons.

It is thought to be the fastest rate of defection from Tesco to its leading grocery market rivals in more than a decade.

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The figures - news of which comes before Tesco's quarterly trading update this morning - suggest that Asda and Morrisons are doing far more damage to Tesco than previously assumed. The data also contradict the widely held view that Aldi and the other discounters Lidl and Netto are proving to be Tesco's toughest competition at present.

Lidl took only a very small amount of business from Tesco in the period, while Tesco actually won sales from the Danish-owned Netto, which, according to recent reports, has handed redundancy notices to the team that finds and buys sites for stores.

The figures also support data published by TNS Worldpanel suggesting that, in the four weeks to November 4, sales were up 9.2 per cent at Asda and 8.2per cent at Morrisons. Tesco was the slowest-growing of the “big four” during the period, with sales rising by 4.2 per cent, with Sainsbury's up by 6 per cent.

In the 12 weeks to November 4, Tesco was again in last place in the growth stakes, with sales up 5.4 per cent. Morrisons was up 9.4 per cent and Asda 9 per cent. Sales at Sainsbury's rose by 6 per cent.

The data indicate that Tesco's much-vaunted launch of about 400 discount brands, seen as a way of fighting off the likes of Aldi and Lidl, may even have backfired.

Industry sources have been critical of the launch - advertising Tesco as “Britain's biggest discounter” - and say that it was imposed by the board rather than being developed by Tesco's marketeers. They also suggest that Tim Mason, Tesco's long-time marketing director, who is now heading Fresh & Easy, its US operation, would have run the campaign better.

Branding Strategy Insider, the marketing blog, said yesterday: “Tesco is attempting to pre-empt an attack on its customer base by becoming more Aldi than Aldi, while retaining its original Tesco strategy, too. We teach this as a failed strategy in business school.”

The news comes as Tesco is expected to report a sharp slowdown in like-for-like sales growth in the September- November quarter. Analysts believe that sales rose only by 1.9 per cent during the three months, which would be Tesco's worst growth figure for 16 years and down from 4.1per cent in the same period last year.

However, as The Times reported on Saturday, Tom Gadsby, an analyst with SG Securities, believes that Tesco sales rose by only 1.3 per cent in the quarter. He has told clients: “The introduction of Tesco's hard discounts range looks to have knocked 3 per cent off sales growth in the quarter. Tesco has been losing market share to both hard discounters and to Asda and Morrisons. Tesco's UK like-for-likes are unlikely to do anything but disappoint.”

The latest till-roll figures from TNS are due on Tuesday of next week and are expected to show a further loss of market share to Asda and Morrisons.

This will raise fears that Tesco's festive advertising campaign, fronted by Des O'Connor, has failed to excite shoppers. Rivals are using younger personalities, with Sainsbury's signing up Ant and Dec to appear alongside Jamie Oliver, its regular star, and Morrisons using stalwarts such as Richard Hammond, the Top Gear presenter. Asda has abandoned use of celebrities this year and is instead showing people in the Yorkshire village of Austwick preparing for Christmas.

Shares in Tesco, which have fallen 40 per cent this year, closed last night down 7.3p at 288p.

A Tesco spokesman said: “Customers are certainly shopping around for bargains, which means they are visiting more stores than they usually would in search of them. So data like this is out of date as soon as it's printed. We know that the work we have done on the new discounter range, on cutting prices and introducing thousands of promotions has attracted significant numbers of new customers to Tesco over the last few weeks.”

— Asda is understood to be bidding for some of Woolworths' stores. Last night, in an interview with Sky News, Andy Bond, Asda's chief executive, refused to comment on speculation, but said that, generally speaking, Asda was committed to expanding.

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