A group of Afghan lawmakers called Thursday for criminal investigations into alleged fraud in the country's disputed presidential election, saying a probe by a U.N.-backed panel has been tainted because some U.N. officials are biased in favor of President Hamid Karzai.

The appeal by about a dozen lawmakers who support Karzai's main challenger, Abdullah Abdullah, was issued after the top American U.N. official here was fired in wake of a dispute with his boss over how to deal with fraud charges in the Aug. 20 balloting.

The official, Peter Galbraith, alleged that the top U.N. envoy in Afghanistan had conspired to conceal the extent of fraud in the election, whose outcome remains unclear due to the fraud charges and a pending partial recount.

"The U.N. office in Kabul is like a campaign office for Karzai," said Ahmad Behzad, a lawmaker representing the western province of Herat. He called on the top U.N. envoy, Norwegian diplomat Kai Eide, to leave the country, telling a press conference that Eide had lost all credibility.

Behzad and the other lawmakers said they wanted anyone believed involved in fraud to be put on trial in Afghan courts. Currently, a U.N.-backed panel investigating the allegations has the power to impose fines or other sanctions but cannot bring a case to court.

Preliminary results show Karzai won the August election with 54.6 percent, but a pending recount could push down those numbers and force a runoff with Abdullah if the incumbent's total falls below a majority.

In a letter to U.N. chief Ban Ki-Moon, a copy of which was obtained by The New York Times, Galbraith said Eide had "for a long time" denied that significant fraud had taken place, "even going to the extreme of ordering U.N. staff not to discuss the matter."

According to the Times, Galbraith said Eide had "blocked me" and other U.N. officials "from taking effective action that might have limited the fraud or enabled the Afghan electoral institutions to address it more effectively."

The letter also accused Eide of giving Karzai the impression that the U.N. was backing him.

Galbraith did not respond to e-mails from The Associated Press, and Eide could not be reached for comment.

A U.N. spokesman in Kabul said the U.N. has remained impartial as it advises Afghans on the election process.

The U.N. mission in Afghanistan "has not and will not turn a blind eye to fraud," spokesman Dan McNorton said. He added that the U.N. "has insisted on slavish, rigorous adherence to the electoral processes. Our neutrality has been and will be paramount at all stages."

In wake of the flap, Afghanistan's major independent monitoring group said it would start looking more closely at the U.N.'s role in the elections. The group, the Free and Fair Elections Foundation of Afghanistan, had previously directly most of its criticism toward Afghan election workers who showed bias toward their favored candidates.

"With this information coming from the media, naturally we would give more attention to it," said Nader Nadery, the head of the group.

Nadery said the monitoring group had not yet seen anything to make it doubt the credibility of the U.N. in the process, but said they had been disappointed that Eide was not more strongly critical of fraud. Reports by monitoring groups suggest as many as 1.5 million votes are questionable because of ballot box stuffing, rigged tallies and other manipulations.

"I didn't see a strong statement coming out of the U.N. I did see (Kai Eide) say there were irregularities. I was expecting stronger language," Nadery said.