Report says a man posing as a Taliban leader who led peace talks was paid and promoted by British intelligence.

Britain's foreign intelligence agency, often referred to as MI6, is said to have promoted an impostor who they believed was a senior Taliban commander touted as key to the Afghan peace process, according to the New York Times.

The Secret Intelligence Service (SIS) agents paid Mullah Akhtar Mohammad Mansour from May this year, believing they had achieved an "historic breakthrough" in forging contacts between the Taliban and the Afghan government, the US newspaper said on Friday.

Agents paid the man several hundred thousand dollars, convinced he had the authority to negotiate with US and Afghan officials on behalf of the Taliban, The Times and the Washington Post reported, citing Afghan officials.

'Wishful thinking'

"Far from being a former Taliban government minister, the individual concerned is now thought to have been a shopkeeper, a minor Taliban commander, or simply a well-connected chancer from the Pakistani border city of Quetta," the New York Times said. The Times said the MI6 flew "Mansour" from Quetta to Kabul on numerous occasions, believing he was second-in-command to Mullah Omar, to take part in "secret peace talks".

Afghan officials told the newspaper that a meeting took place with Hamid Karzai, the Afghan president, in his Kabul palace, although Karzai has denied knowledge of the meeting.

The Times quoted a senior Afghan government official as saying on Thursday: "British Intelligence was naive and there was wishful thinking on our part."

It was believed that the US had helped Britain check the man's bona fides using signal intelligence, the Times reported.

Bill Harris, the former US representative in the southern Afghan city of Kandahar, told the Times on Thursday that it was not British intelligence officers alone who were responsible for the error.

"Something this stupid generally requires teamwork," he was quoted as saying.