WASHINGTON, Nov 26: Afghan President Hamid Karzai’s chief of staff blames the British for inviting a man posing as Taliban leader Mullah Akhtar Mohammad Mansour to Afghanistan for peace talks, the Washington Post reported on Friday.

Afghan intelligence officials told the newspaper that the man was actually a shopkeeper from Quetta. “The last lesson we draw from this: International partners should not get excited so quickly with those kinds of things,” said President Karzai’s aide Mohammad Umer Daudzai. “Afghans know this business, how to handle it.”

But the US media noted that the Afghan know-how didn’t stop the presidential palace from rolling out the red carpet for the impostor, who purportedly met President Karzai himself during the negotiations.

The Americans also are blaming the British, with a senior US official saying that the fake Mullah Mansour was “the Brits’ guy”.

Both Afghans and Americans have hinted that British eagerness to settle the war through diplomacy paved the garden path for the conman from Quetta. Mr Daudzai said that Afghan authorities had contacted a man claiming to be Mullah Mansour’s representative half a year ago, at which point the British took over, arranging for a man they thought was Mansour to be flown to the Afghan palace via Nato aircraft.

A former senior Afghan official countered, however, that the Karzai administration was scapegoating the West for its own botched arrangements.

The embarrassing episode comes as a severe setback to Nato allies hoping to engineer a diplomatic close to the conflict. Britain has not yet formally responded to the allegation.

The Washington Post also reported that British agents paid the man several hundred thousand dollars, convinced he was a top militant with the authority to negotiate with US and Afghan officials on behalf of the insurgents. Britain’s intelligence agency MI6 flew the man to Kabul on numerous occasions believing he was Mansour, an ex-Taliban government minister considered second to Mullah Omar.

Other media reports, however, said that US officials had helped the British check the man’s bona fides using signal intelligence.

The former US representative in Kandahar, Bill Harris, told journalists that the embarrassing mistake was not Britain’s alone, saying “something this stupid generally requires teamwork”.

The US Central Intelligence Agency was reportedly sceptical of British claims. In June, CIA director Leon Panetta said that no serious approaches had been made.

US officials had doubts about the man claiming to be Mansour because “this visitor was a few inches shorter than their intelligence indicated Mansour is, and he didn’t come with the people he said he would bring”, Mr Panetta said. After the story broke on Tuesday in the New York Times, General David Petraeus, the top US commander in Afghanistan, told a press briefing in Germany he was not surprised.

“There was scepticism about one of these all along and it may well be that scepticism was well-founded,” he said.

Gen Petraeus, however, had in October been the first US official to openly say that Nato forces had “facilitated” the passage of what he said were senior Taliban leaders to Kabul.