Foster children face a "postcode lottery" over living standards because the people caring for them are not getting enough money from social services, according to a survey published yesterday.
Allowances for fostered children in more than half of local authorities in England are below minimum acceptable levels, the study by a charity, the Fostering Network, said.
This means fosters carers are left out of pocket and children receive different standards of care depending on where they live.
The survey of 89 local authorities in England found that 56% were paid less than the minimum weekly allowance recommended by the charity; 10% paid the minimum; and 34% paid more.
Researchers said the weekly minimum figure was £103.67 for a baby, rising to £187.60 for a teenager of 16 or older.
Actual allowances paid by local authorities started at £48.52 at week for the youngest children, which is less then half the charity's recommended level.
The Fostering Network is urging the government to introduce a system of national allowances for fostered children based on the organisation's recommended rates.
Gerri McAndrew, executive director of the Fostering Network, said: "This survey shows the extent to which the foster care service is underfunded in England, with allowances clearly falling below the acceptable minimum in many areas."