Mr Appel's predecessor resigned after allegations he evaded taxes

The firm's board named logistics head Frank Appel as its new chief after accepting Mr Zumwinkel's resignation.

Prosecutors said he was suspected of not paying 1m euros (�750,000) in taxes, by using banks in Lichtenstein.

The allegations are part of a wider tax evasion scandal that has grabbed headlines in Germany.

The finance ministry said its investigation was targeting hundreds of suspects believed to have defrauded tax authorities of hundreds of millions of euros through secret bank transactions.

Tax haven

German leaders said they would discuss financial transparency with Liechtenstein's Prime Minister Otmar Hasler when he visits Berlin later this week.

"I will be evaluating very carefully whether we need further initiatives at a European level to break up tax havens," Finance Minister Peer Steinbrueck said.

Mr Zumwinkel is the only suspect to have been named so far. but police raided homes and offices across Germany on Monday.

One of Germany's most influential business figures, Mr Zumwinkel, 63, is credited with transforming the postal service into a logistics giant, as well as developing its retail banking arm, Postbank.

He had been chief executive of Deutsche Post for 18 years.

Mr Appel, 46, joined Deutsche Post in 2000 and had been tipped as a favourite to succeed Mr Zumwinkel.