May.26, 2010, 6:25PM BST

Italy's authorities, which last week said they had been handed the data from French regulators, estimated that around 7,000 Italian clients of HSBC private bank in Switzerland are on the list and may be subject to a tax evasion probe.

A spokesman for HSBC said the bank did "not recognise" the numbers released by Italians.

In March the London-based bank said that a list of 24,000 Swiss clients had been stolen. The bank has said it has not seen the complete list but has warned that the data is "confusing and possibly misleading." For instance, only 15,000 of the accounts listed on the list are current, according to HSBC.

Sources close to the bank insist that there is a wide mix of nationalities involved, none of which make up more than 10pc of the total.

The list was stolen last year by Herve Falciani, a former employee of HSBC in Switzerland. Mr Falciani left Switzerland with the data and returned to his native France, where he then handed the list to authorities.

The French, who started a money-laundering investigation into 3,000 accounts held by French clients thought to be worth around €3bn (£2.54bn), have defended their use of the stolen data on the basis that their work is part of a European and global crackdown on banking secrecy and tax evasion.

The Italian police said in a statement that 6,936 accounts, over a period from 2005 to 2006, were held under 5,728 names, of whom 51pc were entrepreneurs.

Nearly two-thirds of the accounts were held by individuals based in Italy's northern region of Lombardy, while 132 accounts held more than $10m each. The police added that 133 of the account holders were companies and associations rather than individuals

Governments around the world are looking to clamp down on money laundering and tax avoidance in the aftermath of the global financial crisis.

HSBC said it had lost very few clients since the disk was taken.

Swiss bank UBS has seen billions of dollars withdrawn since US authorities investigated it over tax avoidance practices.