The labor union representing U.S. diplomats called Wednesday for the State Department's top auditor to step down pending the results of a congressional investigation into whether he blocked fraud probes in Afghanistan and Iraq for political reasons.

At the same time, the State Department defended the accused official, Inspector General Howard J. Krongard, saying it had no evidence that would back up the allegations.

But the union, the American Foreign Service Association, said Krongard should "surrender day-to-day control" of his office until the "grave allegations of malfeasance," including charges he ignored security lapses at the new U.S. Embassy in Baghdad, are resolved.

"The worse-case scenario in corruption is when it endangers lives," AFSA President John K. Naland said in a statement. "The worse-case scenario in public service is when the watchdog becomes the suspected violator. Both of these allegations have been leveled against Mr. Krongard.

"As long as he maintains day-to-day control, his office's ability to do its vital job with full credibility will be compromised. He should step down until the allegations are resolved one way or another," Naland said.

The statement was released a day after Rep. Henry Waxman, D-Calif., chairman of the House Oversight and Government Reform Committee, sent Krongard a 14-page letter detailing numerous serious accusations against him lodged by seven current and former officials in his office.

"Your partisan political ties have led you to halt investigations, censor reports and refuse to cooperate with law enforcement agencies," Waxman wrote in the letter.

A central theme in the letter is that Krongard, a Republican political appointee, prevented his staff from cooperating with Justice Department probes and refused to send his staff to Iraq and Afghanistan to look into allegations of fraud and wasteful spending involving the more than $3.6 billion the State Department has spent on contracts in the two countries.

In response, Krongard, who has been in Afghanistan and is en route to Iraq, issued a statement saying, "The allegations, as described to me and in certain media reports, are replete with inaccuracies including those made by persons with their own agendas."

Krongard said he has tried to assist other government agencies, while taking care to avoid overlap, and added, "I look forward to cooperating with the committee and receiving the opportunity to respond in full to these allegations."

Deputy State Department spokesman Tom Casey reiterated those comments in addressing the situation on Wednesday.

"We have no information that would substantiate any of these allegations and look forward to the opportunity to have the inspector general talk to the committee about this," he told reporters.