United States aid worth one billion dollars has wound up in the hands of the Taliban and other insurgency groups, according to war analysts and government auditors.

Sub-contractors have reportedly diverted the funds from programmes meant to stabilise Afghanistan.

In fact, the auditors say, graft has gotten so bad that the US government estimates that only about 10 percent of the aid budget actually reaches the people in Afghanistan who need it.

"Right now, corruption is more important than the politics. I have been there (Afghanistan) seven times in the last year and the estimates I have been told are that 20 to 40 percent of the aid funding goes to corruption," Fox News quoted Michael Thibault, co-chairman of Congress's 'Independent and Bipartisan Wartime Commission on Contracting', as saying.

"The problem is the Afghan culture and the subcontracting practices of the companies that do business there," he added.

One company -- DAI of Bethesda, Maryland -- involved in rehabilitation, was forced to pay five million dollars in protection money to Taliban-connected groups.

But those familiar with the country say the scale of the corruption is far wider.

"Virtually every transaction in Afghanistan involves some degree of payoff," says Christine Fair of Georgetown University's Centre for Peace and Security Studies.

She added, "Everyone is getting a piece of the money. If you want to get a clinic built, you have to make sure everyone in the village is paid off."

That is the same assessment that Richard Holbrooke, the special envoy for Afghanistan and Pakistan, gave to President Barack Obama more than a year ago, according to Bob Woodward's book, Obama's Wars.

"All the contractors for development projects pay the Taliban for protection and use of the roads, so American and coalition dollars help finance the Taliban," Woodward wrote.

Fair explained that the practice has become so deeply ingrained in the economic life of the country that it is often a crucial element in events that appear not to be related to corruption.

Told of Fair's analysis, Thibault said, "I agree with her."

Thibauld noted, "Subcontractors usually build in somewhere between 20 and 40 percent mark-up for payoffs. And that money never shows up on the books of the major contractors."