The aid effort in Afghanistan will prove to be "daunting and difficult", Downing Street warned on Wednesday.

Speaking as the British and US government's published a joint document on the magnitude of the aid effort, Number 10 said no-one should be under any illusions about the scale of the task.

The prime minister's official spokesman said that £40 million had already been delivered to aid agencies operating inside Afghanistan - with a further £26 million committed to dealing with the crisis along the border with Pakistan.

He said the publication of the four page document was aimed at underlining the scale of the aid effort and reminding the public that many of Afghanistan's problems existed long before September 11.

To this end, the document states: "Even before September 11 Afghanistan was in the grip of a severe humanitarian crisis. Over two decades of civil war and the worst drought in living memory, compounded by the cruel and incompetent role of the Taliban has meant that for years the people of Afghanistan have suffered."

In Afghanistan, 70 per cent of adults are under-nourished, 30 per cent do not have access to clean water and the average life expectancy is just 46.

Number 10 says that the aid effort will be boosted once the situation on the ground is stabilised.

"The future has to be a more stable Afghanistan and a more secure Afghanistan," said a spokesman.