Klaus Zumwinkel, the chief executive of Deutsche Post, resigned yesterday as a tax evasion investigation that had focused on him widened to include hundreds of individuals.

He left a day after police had mounted raids on his office and home as part of the investigation.

Yesterday reports said that hundreds of people, including prominent figures, were believed to have assets worth about €3.4billion (£2.5billion) concealed in Liechtenstein.

The Süddeutsche Zeitung newspaper quoted judicial sources as saying that officials were looking at about 700 suspects and had prepared 900 search warrants.

A Finance Ministry spokesman said: “Key personalities from our country sought to avoid their duty of solidarity via taxation by practising fiscal evasion to Liechtenstein.” The spokesman would not comment on who was under investigation, saying only that they were “known and unknown, especially people whose revenues are at the high end of the scale”.

The prosecutor in charge of the investigation said that officials were examining “the financial deposits of several hundred” people, in particular with Liechtenstein foundations, that seem to have been created to avoid taxes”.

LGT Group, a bank in Liechtenstein, the small principality between Switzerland and Austria that is widely regarded as a tax haven, had become a focus of the investigation, reports said. The bank's website describes it as “The Wealth and Asset Management Group of the Princely House of Liechtenstein”. One investigator said: “We have taken the bank apart.”

A spokesman for Peer Steinbrück, the German Finance Minister, said that Mr Zumwinkel had offered to leave Deutsche Post. The state-owned KfW bank holds a 31 per cent stake in the German postal business, which is quoted on the Dax stock exchange. Mr Zumwinkel also resigned as chairman of Deutsche Telekom yesterday.

Government sources said that Frank Appel, head of the international mail and logistics division and a board member, would become chief executive of Deutsche Post. Both the Government and the Ver.di trade union favour Mr Appel, although John Allan, Deutsche Post's chief financial officer, is also a contender.

Deutsche Post's supervisory board will meet on Monday to decide on the management change.

German media reported yesterday that Mr Zumwinkel had transferred millions of euros to a bank in Liechtenstein to evade German taxation. The 64-year-old had been at the helm of Deutsche Post since 1990, when it was state-owned. His tenure has made him the longest-serving chief executive in the Dax index. The group, which is active in overseas markets, including Britain, was floated in 2000.

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