The British ambassador in Kabul thinks the war in Afghanistan is as good as lost and that current US military and economic strategy there is destined to fail, according to a potentially explosive report leaked yesterday by French sources.

The British ambassador in Kabul thinks the war in Afghanistan is as good as lost and that current US military and economic strategy there is destined to fail, according to a potentially explosive report leaked yesterday by French sources.

Sir Sherard Cowper-Coles, the UK diplomat involved, is also alleged to have said that the only practical long-term solution was for the West to support "an acceptable dictator" to unite the fractured country.

The diplomatic bombshell, immediately played down by the Foreign and Commonwealth Office, came on the same day that the senior American military commander in Afghanistan called on Nato to provide more troops and other aid "as quickly as possible" in a counterinsurgency battle he said could get worse before it gets better.

The general's downbeat assessment also coincides with a fresh report by UN Secretary-General Ban Ki-moon, who expressed dismay that attacks on aid workers have risen in 2008 despite the presence of more allied troops than at any time since the US-led invasion in 2001.

The allegedly critical British summary came from direct quotations from a cable written by François Fitou, the French deputy ambassador in the Afghan capital.

Mr Fitou reported to President Sarkozy's office that Cowper-Coles believed "American strategy is destined to fail" and that the government of President Hamid Karzai had "lost all trust" among the Afghan population.

The French diplomat is reported to have summarised the British ambassador's main points from a September 2 meeting. His cable, quoting Cowper-Coles, said: "The current situation is bad. The security situation is getting worse. So is corruption and the government has lost all trust.

"Our public statements should not delude us over the fact that the insurrection, while incapable of winning a military victory, nevertheless has the capacity to make life increasingly difficult, including in the capital.

"The presence - especially the military presence - of the coalition is part of the problem, not the solution. The foreign forces are ensuring the survival of a regime which would collapse without them. In doing so, they are slowing down and complicating an eventual exit from the crisis."

Mr Fitou sent the cable to brief President Sarkozy and Bernard Kouchner, the French Foreign Minister, ahead of meetings with Britain and other Nato allies .

Cowper-Coles, 53, was also quoted as saying that while Britain had no alternative to supporting the United States, the Americans should be told to change strategy.

Reinforcing the military presence against the Taliban insurrection would be counter-productive, he said, and allied governments should start preparing public opinion to accept that the only realistic solution for Afghanistan was to be ruled by "an acceptable dictator".

The FCO would not comment directly on the report, but a spokesman said that the remarks did "not accurately reflect" the views of the ambassador or his deputy.