The police issued a statement on Thursday announcing that that they are looking for Heinrich Kieber, a 42-year-old Liechtenstein citizen and former employee of LGT Bank.

"Mr Kieber is subject to an international arrest warrant. The Liechtenstein law enforcement agencies demand his immediate extradition," the statement announced.

Kieber, who worked for LGT Treuhand, a subsidiary of Liechtenstein's LGT bank which set up and managed foundations for clients, was understood to have received a sum of about EUR4.5mn from the German intelligence services for information about wealthy German clients contained on a computer disc, stolen by him in 2002.

It is believed that the disc contained the names of 1,400 of the bank's clients, about 600 of whom were German, and prosecutors there have claimed that their investigation has led to 163 arrests and the recovery of more than EUR27 million in tax revenue.

However, the affair has had widespread international significance, and sparked perhaps the largest global tax evasion investigation of modern times, as well as a new debate on bank secrecy laws in places such as Liechtenstein and Switzerland.

It has been reported that the UK tax authority paid Keiber GBP100,000 (USD203,000) for access to information about Britons who may have undeclared assets with the bank, while revenue authorities from a growing list of other countries have also launched investigations into their citizens' involvement with Liechtenstein banks, including Austria, Australia, Canada, France, Greece, Italy, New Zealand, Spain, Sweden and the United States.

For its part, Liechtenstein has strongly condemned the actions of the German and other governments, accusing them of violating its sovereignty. It has also pledged to tighten privacy rules, rather than loosen them as is being demanded by governments across the world, in response to the affair.

The precise whereabouts of Keiber are currently unknown, although some newspapers claim to have tracked him down to the northern Australian city of Cairns.

According to the German weekly Focus, he is still communicating with the German intelligence service and, apparently fearing for his life, has implored them to better protect his identity and help him establish a new life in South America.