Peter Galbraith, who spent time in Afghanistan representing the UN, speaks to the Vermont legislature in January 2007. (Toby Talbot/Associaated Press)

The United Nations has denied allegations made by one of its former senior officials in Afghanistan that its mission there was biased in favour of President Hamid Karzai.

Peter Galbraith, the UN's former No. 2 official in Afghanistan, was sacked last week after accusing his boss of turning a blind eye to fraud that helped Karzai win the Aug. 20 presidential elections.

"The election was characterized by massive fraud," Galbraith told CBC News from the UN in New York. In certain provinces in the south, for example, there were as many as four to 10 times votes recorded as voters actually appeared," he said.

"By some calculations, up to 30 per cent of the vote for President Karzai were fraudulent."

Preliminary results released last month showed Karzai won the election with 54.6 per cent of the votes, enough to avoid a runoff with second-place finisher Abdullah Abdullah, his former foreign minister.

But the recount and audit ordered by a UN-backed fraud panel could cut Karzai's votes below the 50 per cent threshold needed to win outright.

About 13 per cent of the country's approximately 26,300 polling stations are considered questionable by the fraud panel because they had more than 100 per cent turnout or more than 95 per cent of votes for one candidate.

With files from The Associated Press