HSBC says Swiss data theft affects 15,000 clients

Herve Falciani, a former HSBC computer specialist, has admitted stealing client data from the bank which he passed to French tax authorities.

HSBC said in December an ex-employee had stolen data from its Swiss private bank's headquarters in 2006 and 2007 but, to the best of its knowledge, fewer than 10 clients were involved.

HSBC said on Thursday that Swiss authorities said they would not support use of the stolen data to answer requests from foreign authorities about tax issues.

"It is now clear that 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.

The stolen client information was limited to accounts in Switzerland, excluding ex-HSBC Guyerzeller accounts.

(Reporting by Steve Slater; Editing by Dan Lalor)