The Taliban is back in control of large parts of Afghanistan, according to a research group based in the state.

The Senlis Council claims insurgents have established a permanent presence in more than half of the country and they predict the Taliban will emerge in the capital Kabul.

Despite the huge international and military effort against the Taliban, the Senlis Council claims there is a "serious" danger they will regain control of the state.

The think-tank warns that the security situation has reached "crisis proportions", and the Taliban's resurgence across the state has been "proven beyond doubt".

The report says: "The insurgency now controls vast swaths of unchallenged territory including rural areas, some district centres, and important road arteries.

"The Taliban are the de facto governing authority in significant portions of territory in the south and east, and are starting to control parts of the local economy and key infrastructure such as roads and energy supply."

The report adds: "The insurgency also exercises a significant amount of psychological control, gaining more and more political legitimacy in the minds of the Afghan people who have a long history of shifting alliances and regime change."

The researchers highlight growing lawlessness in the border areas with Pakistan, an "almost endless" stream of recruits driven by poverty, and ideological support from al-Qaeda as important factors.

Often Nato and Afghan Government forces fight battles for territory which turn out to be "pyrrhic" because they have no way of defending it.

The report adds: "The depressing conclusion is that, despite the vast injections of international capital flowing into the country, and a universal desire to 'succeed' in Afghanistan, the state is once again in serious danger of falling into the hands of the Taliban.

"It is a sad indictment of the current state of Afghanistan that the question now appears to be not if the Taliban will return to Kabul, but when this will happen and in what form."

The report recommends that the size of the Nato force should be doubled from 80,000 "as soon as is logistically possible".

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