Afghan President Hamid Karzai has demanded that all detainees being held by British forces in the restive south be handed over within two weeks, saying that holding prisoners any longer would be a violation of sovereignty.
The British government came under fire earlier this month when it emerged that up to 90 suspected insurgents were being held without charge at Britain's main base in southern Afghanistan.
British forces are normally allowed to hold suspects detained in Afghanistan for 96 hours, but they can be held for longer in "exceptional circumstances", such as to obtain critical intelligence.
"Any continuation in detention of these prisoners by British forces will be a violation of Afghanistan's national sovereignty and laws," Aimal Faizi, Karzai's spokesman, said in a statement released late Saturday.
Faizi said that a June 22 deadline for the handover had been set and that the British embassy in Kabul had been informed.
Britain said on Thursday that it would restart transferring detainees after suspending the process last November due to claims of abuse of prisoners in Afghan custody.
Karzai has made the issue of Afghans held by foreign forces a symbol of national independence before he steps down next year and as US-led combat troops wind down more than a decade of war.
The United States handed over full control of Bagram prison in March after months of lobbying from Karzai.