Every Syrian refugee who comes to Britain will cost taxpayers up to pounds 24,000 a year, according to official figures which suggests the total bill is likely to rise to hundreds of millions of pounds.
A leaked Home Office document has revealed that the cost to the taxpayer for taking refugees will range from pounds 10,720 for children to pounds 23,420 for unemployed adults. The figures emerged as David Cameron said that Church of England bishops who had called on him to accept more refugees were "wrong". Mr Cameron has pledged to take 20,000 Syrian refugees over the next four and a half years, but 84 bishops have said Britain should accept 50,000.
A major offensive on the city of Aleppo by forces loyal to the Assad regime has caused tens of thousands of Syrians to flee their homes over the past few days alone. The Prime Minister said: "I would now like to see the bishops make a very clear statement, which is Britain has fulfilled our moral obligations by making a promise to the poorest countries and poorest people in the world of spending 0.7 per cent of our gross national income on aid, and how many other of the big countries that made that promise have kept that promise?"
The Home Office figures, obtained by the BBC, revealed that the cost to the taxpayer of taking in Syrian children ranges from pounds 10,720 for under-threes to pounds 16,220 for those between the ages of five and 18.
Syrian adults, who have access to weekly benefits, cost even more unless they are allowed to work. According to leaked local government figures, each Syrian adult costs taxpayers pounds 23,420 - or pounds 10,720 if they are in work.
The cost per Syrian refugee to local councils is estimated to be pounds 8,520 per person. On top of this, central government will be forced to pay pounds 12,700 in benefits and pounds 2,200 for medical care.
An estimated 70,000 Syrians have fled their homes in the southern Aleppo countryside since Friday as regime troops and Russian warplanes launch an assault on rebels holding much of Syria's second city.
Forces loyal to Bashar al-Assad, the Syrian president, have moved in on the shattered city from three sides, backed by Russian warplanes, Iranian ground troops, and a constellation of militia fighters hailing from the Lebanese Hizbollah movement and smaller groups sponsored by Iran.
"People are scared to death, everyone is on the move," said Dr Zaidoun al-Zoabi, the head of the Union of Syrian Medical Relief Organisations, as he returned from the southern Aleppo countryside. "People are sleeping in the streets, on sidewalks, in the fields, but there is nowhere for them to go."
On Sunday, the Turkish prime minister, Ahmet Davuto?lu, called for international action to prevent a new wave of refugees from moving north across the Turkish border.
The Syrian Network for Human Rights, a monitoring group, said there had been "massive displacement" in recent days. An aid worker in southern Aleppo said that several villages stood almost empty. "The strong travel on foot, pushing the elderly in wheelbarrows," said the aid worker, speaking on condition of anonymity. "It is the most desperate thing."
Those left behind face severe medical shortages after two hospitals serving the area's 350,000 residents were damaged by Russian air strikes. In the town of al-Hader, a neo-natal unit was hit, prompting a frantic rush to evacuate new-born babies.