UNITED NATIONS - UN electoral officials said Wednesday that suspect ballots in Afghanistan's presidential election are being audited for fraud and a final result is not expected before the end of next week. Afghans voted on August 20 for a president and provincial councillors but the elections have been overshadowed by allegations of fraud, and controversy over the role of the UN in keeping the process clean. Most of the allegations have been directed against incumbent Hamid Karzai, including findings by European Union observers that a quarter of all votes, or 1.5 million, were fraudulent. Karzai leads the preliminary results with around 55 percent of the vote. He needs 50 percent plus one vote to be declared the winner. His main rival, Abdullah Abdullah, has around 28 percent and hasbeen at the forefront of vote-rigging accusations against Karzai. Observers -- including sacked former deputy UN special envoy to Afghanistan, Peter Galbraith -- have said 30 percent of Karzai's votes were fraudulent. The audit being conducted at the Independent Election Commission (IEC) just outside Kabul aims to determine the level of fraud and whether or not a run-off is needed between Karzai and Abdullah. To do this, 10 percent of ballots in 3,498 ballot boxes are being examined for evidence of tampering and ballot-stuffing. The UN officials told a press conference in New York that Galbraith has a "personal agenda" and was fired from the U.N. mission because of an "accumulation of circumstances" that showed he was not the right person for the job. Assistance Secretary General for Peacekeeping Operations Edmond Mulet said those included Galbraith's proposal to address election fraud by annulling the elections and setting up a transitional government. Mulet said such an action would be "completely out of bounds" with the United Nations mandate in Afghanistan. The Washington Post said Wednesday that confidential UN data shows substantial discrepancies, with vote counts in some provinces exceeding actual voters by more than 100,000. The audit being conducted at the Independent Election Commission (IEC) just outside Kabul aims to determine the level of fraud and whether or not a run-off is needed between Karzai and Abdullah. To do this, 10 percent of ballots in 3,498 ballot boxes are being examined for evidence of tampering and ballot-stuffing. The paper cited a spreadsheet kept secret by the United Nations' chief envoy in Kabul, Kai Eide, who has been under pressure to release details of what his sacked former deputy, US diplomat Peter Galbraith, described as "very extensive" voter fraud in the August 20 election. The UN data obtained by the Post showed major discrepancies between actual voter turnout and the results, particularly in provinces where President Hamid Karzai won by wide margins. In the southern Helmand province, where 134,804 votes were recorded -- 112,873 of them for Karzai -- the United Nations estimated that just 38,000 people voted, and perhaps as few as 5,000, the newspaper reported. In Paktika province, while 212,405 valid votes were cast according to Afghanistan's Independent Election Commission, including 193,541 for Karzai, the United Nations estimated that just 35,000 people voted. Kandahar province recorded 252,866 votes, including 221,436 for Karzai, but the UN voter estimate was 100,000. And in several provinces won by Abdullah Abdullah, Karzai's main challenger, the global body estimated larger turnouts than those recorded by election officials. In Balkh province, the United Nations estimates 450,000 people voted, but results showed 297,557 votes. The Post reported that a UN spokesman in Kabul, Dan McNorton, did not dispute the authenticity of the spreadsheet but cautioned that "the information that you have is unsubstantiated raw data and should be treated as such." But in comments to the Post, Galbraith said the data was critical to assessing the credibility of the election and should have been handed over to Afghan officials and international election monitors, but that Eide refused. "I think we did an excellent job at collecting data," the Post quoted him as saying. "We collected it with the idea of assisting the Afghan legal party that was investigating fraud, but Kai opposed turning it over." Galbraith has described Eide as being biased in favor of Karzai.