Josef Ackermann, the chief executive of Deutsche Bank, came under renewed pressure to resign today after a top German court ruled he should face a retrial over controversial bonus payments made to executives in Vodafone's £100 billion hostile takeover of Mannesmann five years ago.

Mr Ackermann, who signed off multi-million pound bonuses including to Mannesmann chief executive Klaus Esser after the German engineering group gave up its battle against the takeover, now stands accused for a second time of failing in his duty by approving the payments.

Mr Ackermann, along with five former members of the Mannesmann board, has already been cleared once of overpaying executives by as much as €60 million (£40.7 million). But today's ruling, which also covers the former Mannesmann executives, overrules the earlier judgment, by a lower German court.

Klaus Tolksdorf, the judge presiding over the latest ruling, said that in the new trial Mr Ackermann would be accused of violating shareholders' trust by approving the payments.

Mr Esser was awarded a further £10 million bonus on top of the £10 million that was stipulated in his employment contract he should receive in the event of a takeover.

Vodafone successfully bought Mannesman in 2000 after a fierce hostile takeover battle.

Deutsche Bank said later that it "regrets" the decision of the court to overrule the first verdict and once again expressed its "unrestricted trust" in Mr Ackermann.

"It also conveys its respect to Dr. Ackermann for the way in which, despite the additional burdens caused by these proceedings, he has devoted his efforts unswervingly and with great success to the interests of Deutsche Bank," the bank added.

The bank has always backed Mr Ackermann, and rebuffed suggestions he might resign. However, speculation has been growing that Mr Ackermann himself might want to avoid further embarassment for the bank.

The original trial sparked a frenzy of media interest and intense speculation that Mr Ackermann would be forced to step down. As Germany's most powerful banker, who has led Deutsche Bank for just three years, he was also facing public scrutiny over the domestic and international performance of the bank.

Pictures showing Mr Ackermann's V-for-victory gesture at the first trial caused an outcry in Germany for its Churchillian associations.

According to AFX, one shareholder group has already called on Mr Ackermann to resign. Juergen Kurz, a spokesman for The DSW Association for the Protection of Shareholders told the agency that "the damage for the bank will be even bigger" if Mr Ackermann stays on.

However, Germany's securities regulator BaFin made plain its view that Mr Ackermann should be "presumed innocent". Jochen Sanio, the president of BaFin, said: "Only if a manager of a financial institution were to be finally convicted by a criminal court would BaFin think about ending his professional career."

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