The pressure on Paul Wolfowitz, the President of the World Bank, grew today as Germany's governor to the global financial institution added her voice to calls for his resignation.

Heidemarie Wieczorek-Zeul, who is also the German Development Minister, said that the credibility of Mr Wolfowitz and of the World Bank itself had been "thrown into doubt" following the controversy over disclosures that he engineered a promotion and a pay rise of nearly $200,000 (£100,000) for his girlfriend, Shaha Riza, in 2005.

Ms Wieczorek-Zeul said that Mr Wolfowitz's refusal to resign was "no longer acceptable".

"My conclusion is that Wolfowitz should do the bank a service and take the consequences himself. And the sooner, the better," she said.

Ms Wieczorek-Zeul's comments, at a press conference in Germany, echo fears expressed earlier today by former senior World Bank staff who said they "believe that he [Mr Wolfowitz] can no longer be an effective leader".

In a letter to the Financial Times, they said the World Bank had to retain its credibility "if it is to speak with the moral authority necessary to move the poverty agenda forward".

"There is only one way for Mr Wolfowitz to further the mission of the bank: he should resign," they said.

Mr Wolfowitz's future looks increasingly precarious, particularly since the Bank's 24 executive directors met on Friday to discuss the situation and make public their concerns.

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