The British and United States-led international coalition in Afghanistan has "failed to achieve stability and security", an international report said today.
The country is "falling back into the hands of the Taliban" because of the West's failure to address Afghans' "extreme poverty", according to the study for the Senlis Council.
The council is an international policy think tank whose work encompasses Western foreign policy in relation to security, development and counter-narcotics measures in Afghanistan.
All of southern Afghanistan, where British troops are concentrated in the lawless Helmand province, is now under "limited or no central government control", the report claims.
The council blames the international forces' military priorities and "flawed" poppy-eradication policies for Afghanistan's plight half a decade after operations began in October 2001.
The report says: "Five years after their removal from power, the Taliban is back and has strong psychological and de facto military control over half of Afghanistan .
"Having effectively assumed responsibility for the country in 2001, the United States-led international community has failed to achieve stability and security in Afghanistan."
The study, entitled Afghanistan Five Years Later: The Return of the Taliban, comes a day after the British army's most senior officer warned his men were fighting at the limit of their capacity.
Helmand is a huge producer of opium, and one of the tasks of British troops in the province is supporting local Afghan counter-narcotics forces in tackling the illegal drugs trade.
But today's report claims destroying poppy fields is perceived as an "anti-poor policy" and fuels violence and insecurity to the Taliban's advantage.
The 248-page report also warns of a "growing hunger crisis" in southern Afghanistan that is driving many people into "makeshift, unregistered refugee camps".
The council recommends making emergency poverty relief a top priority, overhauling "failed" anti-poppy strategies and insisting that military objectives take a back-seat to development in the country.