Cluster bombs can spread shrapnel over large areas
"There must be an urgent rethink of this action. There is evidence from Kosovo and the Gulf War that the components of these weapons are prone to missing their targets and fail in significant numbers to explode.
"They then pose a serious long-term threat to civilians and ground forces alike," he said.
Mr Purkis' call was echoed by director of aid agency Landmine Action Richard Lloyd, who said that the Afghan people already faced the overwhelming threat of starvation.
"The presence of highly sensitive unexploded cluster munitions will increase the number of casualties caused by the severe landmine problem in Afghanistan for years to come, and will deny people facing starvation the use of their land," he said.
Hidden danger
Cluster bombs each contain about 200 smaller bomblets weighing 1.5 kilograms, which are designed to spray out shrapnel and set fire to any combustible material nearby.
Officials from the United Nations Mine Clearance Programme also appealed to the United States for information about the cluster bombs dropped on Monday night around the northwestern city of Herat in Afghanistan.
Civilians in villages close to Herat reported seeing several unexploded cluster bombs - recognisable by their yellow markings.
Mine-clearing teams in Afghanistan are only able to identify and destroy cluster bombs with difficulty and at great danger.
Villagers afraid
UN officials say they need information on where the bombs were dropped and how to safely clear them so that villagers may leave their homes.
Dan Kelly, manager of a UN mine removal programme in Afghanistan, said on Wednesday that the bombing had left people near Herat afraid to venture from their homes and effectively trapped within their villages.
"The villagers have a lot to be afraid of because these bomblets, if they did not explode, are very dangerous," he said.
"And they can explode if the villagers so much as touch them."
The cluster bombs fell during a US attack on Monday night. United Nations officials had already confirmed a military hospital, a nearby village and a mosque in a military camp were hit in the attack.
So far nine people are confirmed dead in the raids on Herat since Monday.
The Taleban say that up to 1000 civilians have been killed since bombing raids began. However, the Pentagon has denied such figures.