Widespread and systematic fraud during the Afghan presidential elections has tarnished the legitimacy of any future government and undermined the Nato campaign there, Western and Afghan officials have admitted.

Two more British soldiers were killed yesterday and the commander of the Nato forces in Afghanistan warned President Obama that the eight-year war was in a “serious” state and that big changes were needed if victory was to be achieved.

General Stanley McChrystal is understood to have recommended in a strategic review that counter-insurgency efforts be focused on protecting civilians rather than fighting militants.

August was one of Nato’s bloodiest months in Afghanistan, with 74 soldiers killed. More than 300 have died so far this year, making 2009 the worst year for Western forces since the Taleban were overthrown.

The latest British casualties — killed by a bomb while on foot patrol in Helmand — were from 3rd Battalion The Royal Regiment of Scotland. They bring to 19 the number of British troops killed in August.

David Kilcullen, one of the architects of Nato’s anti-insurgency campaign, said that the failure of the Afghan Government to provide basic services in many areas was allowing the Taleban to establish its own courts, hospitals and security. “A government that is losing to a counter-insurgency isn’t being outfought, it is being outgoverned,” he said.

There have been more than 2,500 complaints about the August 20 vote, 691 of them involving serious charges of vote rigging, meaning that they could affect the overall outcome of the election.

One international election observer, who asked not to be named, said: “The pattern is of systematic and widespread fraud, which really does call into question the legitimacy of the election. This is large scale and it is across the country.”

Ahmad Nader Nadery, head of the Afghan Free and Fair Election Foundation, said the scale of the vote rigging was serious. The fraud presents Washington with a dilemma: to back President Karzai, who is already seen as an unreliable partner, after a disputed and discredited first-round victory or to force a second-round run-off. The latter could lead to months of political paralysis and a rapid erosion of support for a war that less half of Americans now view as worthwhile.

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