Documents released by the bank's ethics committee show Wolfowitz, controversially appointed to the World Bank from the Pentagon, where he was one of the leading architects of the Iraq war, tried unsuccessfully to limit access to employee salary information after the bank launched an internal inquiry into the affair.

If it can be shown that Wolfowitz acted improperly by helping his lover, Shaha Riza, to a pay rise and a highearning post in the US state department, then he is expected to pay with his own job. Earlier this month the bank ordered a special committee to advise on Wolfowitz's future, and widened the scope of the inquiry to look into appointments of staff to his private office. Today he is due to meet members of the inquiry committee.

But now it emerges that, in a letter written in response to a "brief conversation" dated 13 July 2006, bank vice president Xavier Coll told Wolfowitz that it was "virtually impossible" to shut off access to individual salary details, although some staff had had their access "revoked".

The news will come as a further blow to the embattled bank chief, who has been accused of acting with "reckless disregard" of his duties and offering "outlandish compensation packages to the people closest to him". This month, 32 anti-corruption officials said in a letter that he was a liability, and called for "clear and decisive actions" to resolve the issue.

The bank's staff association has also demanded that he quit.

"We are deeply concerned by the impact of the current leadership crisis on the bank's credibility and authority, " 46 employees said on Friday in a letter to Wolfowitz and the bank's board. "Our own governance standards must be upheld and enforced impartially and without exception, even when they touch the highest levels of this institution."

The former US deputy defence secretary has made fighting corruption a hallmark of his tenure, suspending loans to countries including Chad and India because of concerns that the money might disappear into the pockets of politicians.

In their letter, the members of the Washington-based agency's governance and anti-corruption strategy group said the "credibility of our front-line staff" had been undermined. They asked the board "to resolve this crisis quickly in a way that demonstrates to all our stakeholders the bank's commitment to the highest standards of integrity".

Wolfowitz initially offered to recuse himself from dealings with Riza, a request that was rejected by the board's ethics committee, according to his lawyer, Robert Bennett. His subsequent decision to promote and reassign her was made with the approval of the committee, Bennett said.