Britain’s biggest bank, HSBC, is carrying out a review of 300,000 current accounts for evidence of fraud as consumer groups warn that banks and retailers are leaving customers vulnerable.

The alert follows concern about lax security at Indian call centres. Undercover researchers working for ITN and Channel 4 found evidence of a roaring international trade in customers’ details whereby call-centre employees with access to the data sell them on to criminals for a profit.

Many of Britain’s big banks have moved their call centres to India to take advantage of the cheap, well-educated workforce.

HSBC denied that customer details had been leaked from its Indian call centres, but is nevertheless checking accounts for evidence of fraudulent use.

HSBC said: “There has been absolutely no leak of customer data from HSBC’s operations in India.”

Its review of 300,000 accounts has resulted in 27,000 customers receiving notification that their accounts will be closed in 30 days.

In some cases this is because the bank found evidence of fraudulent use unrelated to India, but in others customers have been caught out because they were not complying with the account rules, such as minimum funding requirements.

Meanwhile, Which, the consumer lobbyist, has issued a warning about fraudsters exploiting a security loophole on self-service tills in Tesco supermarkets.

The Which warning was prompted by reports of credit and debit-card holders being left hundreds of pounds out of pocket after having their cards copied and used at Tesco stores by crooks.

Card fraud of this type has fallen since the introduction of chip-and-pin technology that requires cardholders to enter a pin rather than sign their name to verify a purchase.

Overall card fraud losses dropped from £743m in 2004 to £647m last year, according to figures from Apacs, the payments clearing association, despite many criminals turning to internet and telephone card fraud instead.

But Tesco is yet to introduce chip-and-pin card readers at the self-service tills available in more than 300 of its stores. Shoppers can therefore scan in their groceries and then pay for them using a card without having to enter a pin or even sign their name.

Those affected by the scam so far have been refunded by their banks, but Which? researchers were appalled by how easy it was to buy goods using someone else’s card and are therefore calling on Tesco to update its self-service tills.

Neil Fowler of Which said: “It’s hard to believe that Britain’s biggest supermarket is making it so easy for criminals to use stolen credit cards in its stores. We think it’s highly irresponsible. As a company that prides itself on caring about its customers, we can only hope that Tesco closes this obvious loophole and introduces standard security procedures in the very near future.”

Tesco denies that there is a big problem with fraudsters mis-using its self-service tills and said that chip-and-pin technology would be in place by the end of the year.

A Tesco spokesman said: “When we originally introduced the self-service tills more than two years ago, chip-and-pin was not a proven technology. Now that it has become widely accepted, we will be rolling it out into all 320 stores where the tills are used. This process has already begun and should be completed by December.”

Measures you can take to protect yourself against fraud include shredding bank statements, bills and direct mail before throwing them away.

A recent report from insurer CPP revealed that millions of Britons leave themselves open to identity fraud on average 35 times a week, largely by failing to safely dispose of bank statements, receipts and other unwanted documents.

For more on consumer affairs visit www.timesonline.co.uk/consumeraffairs