HSBC says thousands of customers were affected by data theft

Former IT employee tried to sell stolen customer details for more than £2m

The privacy of some HSBC customers is under threat

A former HSBC employee stole client data from the bank affecting up to 24,000 customers in Switzerland, it emerged today.

“The theft, which was perpetrated by a former IT employee about three years ago, involves approximately 15,000 existing clients who had accounts with the bank in Switzerland before October 2006,” HSBC said in a statement.

However, reports suggest that an additional 9,000 accounts were also affected.

Ex-staffer Herve Falciani copied the data onto a personal computer and left for France while under investigation. He was allegedly trying to sell the data for more than £2m.

Back in December, HSBC said that fewer than 10 clients were affected by the thefts, which took place in 2006 and 2007.

HSBC has been in touch with the customers concerned. The bank believes the stolen data will not allow unauthorised people to access those accounts, despite the fact that the incident could mean that some of the account holders affected could be risking prosecution by tax authorities.

"We deeply regret this situation and unreservedly apologise to our clients for this threat to their privacy," said Alexandre Zeller, chief executive of the Swiss subsidiary.