The official version of the US-led campaign in Afghanistan received a blow today with a leaked report that the British Ambassador in Kabul believes that US strategy is wrong and the war is as good as lost.

    The potentially explosive views were published by Le Canard Enchaîné, a respected French weekly, which said that they were direct quotations from a diplomatic cable written by François Fitou, the French Deputy Ambassador in Kabul.

    Mr Fitou reported to President Sarkozy's office and his own Foreign Ministry that Sir Sherard Cowper-Coles, the British Ambassador, believed that "American strategy is destined to fail" in Afghanistan, according to the newspaper.

    It published a reproduction of what it said was the coded cable, in which the French diplomat summarised the ambassador's main points from a September 2 meeting.

    "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 (which, moreover, will probably be dramatic)."

    The French diplomat sent the cable to brief President Sarkozy and Bernard Kouchner, the Foreign Minister, ahead of meetings with Britain and other Nato allies over the Afghan deployment. The French deployment of some 3,000 troops there has become intensely unpopular since 10 soldiers were killed in an ambush near Kabul in August.

    The allies have been thrown on the defensive over the past 18 months by the resurgence of the Taleban rebel forces, who have moved close to Kabul, where the Government of President Karzai is struggling to establish its authority.

    Sir Sherard, 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 Taleban insurrection would be counter-productive, he said, according to Le Canard. "It would identify us even more clearly as an occupying force and it would multiply the number of targets (for the insurgents)," he was quoted as saying.

    The allied governments should start preparing public opinion to accept that the only realistic solution for Afghanistan was to be ruled by "an acceptable dictator".

    "In the short term we should dissuade the American presidential candidates from getting more bogged down in Afghanistan," the ambassador was quoted as saying.

    The Foreign and Commonwealth Office would not comment directly on the leaked French diplomatic report, but a spokesman said that the remarks did "not accurately reflect" the views of the ambassador or his deputy.

    "We are committed to working in support of the Government of Afghanistan in order to deliver solutions to the challenges facing the country through civilian and military efforts," said a spokesman.

    He said that Britain would continue to work closely with Kabul and that success in Afghanistan was a "long term" goal.

    Although it is understood that the meeting between Sir Sherard and the French envoy to Kabul did take place, the version of events contained in the diplomatic cable is regarded in Whitehall as a "parody" of what was said.

    The British side is particularly dismayed that they reportedly support a dictatorship in Afghanistan. Insiders insist these words were never uttered. There is a suspicion that the British position was deliberately "exaggerated" to produce a version that Paris wanted to hear.