A man purporting to be one of the most senior Taliban commanders – who held secret meetings with NATO and Afghan officials – was apparently a fake, according to reports in the US.

The conman, who claimed to be Mullah Akhtar Muhammad Mansour – thought to be second in the Taliban hierarchy under the founder Mullah Mohammed Omar – may not even be Taliban at all, according to the New York Times.

The paper quotes a Western diplomat in Kabul, who was closely involved in the discussions saying “It’s not him… and we gave him lots of money”.

The Washington Post says some Afghan officials now believe the man who tricked his way into negotiations is just a shopkeeper from Quetta in Pakistan, where some of the Taliban leadership is thought to be exiled.

In the last few months, American officials and even General Petraeus have alluded to their talks with the Taliban as a sign that the insurgents were interested in negotiating an end to the war.

“Do not accept reports by foreign media regarding our meeting with Taliban leaders, it is all publicity and lies.” President Hamid Karzai

The man now thought to be an imposter was given money and flown to Kabul on NATO planes to hold talks on three occasions. He was even said to have met Afghan President, Hamid Karzai, though in a news conference in the Presidential palace today, Karzai denied that his government had met anyone named Mansour.

“Do not accept reports by foreign media regarding our meeting with Taliban leaders, it is all publicity and lies,” he said.

An Afghan minister with responsibility for reintegrating insurgents last month played down the significance of the talks, characterising them as little more than “networking”.

Who’s fooling who?

In public, the leadership of the Taliban maintains that they are not involved in talks at any level. Mullah Omar recently released a message denying the existence of negotiations, saying “the cunning enemy which has occupied our country, is trying, on the one hand, to expand its military operations on the basis of its double-standard policy and, on the other hand, wants to throw dust into the eyes of the people by spreading the rumours of negotiation.”

Now, embarrassed NATO and Afghan officials are left wondering if it’s actually the Taliban who are the cunning enemy. Could the man have been a Taliban agent?

The New York Times quotes one senior Afghan involved in the story as saying: “The Taliban are cleverer than the Americans and our own intelligence service. They are playing games.”

It’s not clear how much money the fake Mullah Mansour was paid to keep coming back for talks, or why those he met are now so sure he’s not who he claimed to be.

Here, the Guardian spoke to a western official in Kabul who said the blunder had been known about for some time.