Pupils receiving free school meals are having to chip in their own cash - or go without an adequate meal, according to government-commissioned research.
Many schools have been left short of cash as a result of the delegation of meals funding from councils. Some schools have had to put up prices, others have cut back on quality, the report School meals funding delegation by Pamela Storey and Mano Candappa of the Institute of Education, London, says.
Other schools have stopped meals services or increased the number of popular but unhealthy options, such as chips, to make ends meet.
The research is published amid growing concern about children's health.
Last week, an official report called on the Government to improve school meals to halt the rise in obesity.
Twelve local authorities were studied for the report which found that while some schools benefited from delegation, others had had to raise funds to keep cafeterias open.
More than half a million pupils in England are entitled to free school meals. However, many schools have found the cash allocated to these pupils has failed to keep up with rising meals costs.
There is no national figure for how much authorities or schools should spend on free meals but it can range from little more than pound;1 to just under pound;2.
Most secondaries have cash cafeterias where pupils on free school meals pick an option within their allowance or stump up the difference themselves. The report says pupils can often afford little more than a sandwich, so many opt for more filling, but less healthy, options such as chips.
Most primaries have fixed-price lunches so that pupils receiving free school meals can afford the same food as others.
Over the three years since delegation price rises of up to 50p have been common in schools with cash cafeterias, the report says.
In one secondary school, pupils, teachers and kitchen staff complained that prices rose in the cafeteria several times but the purchasing power of pupils on free school meals did not.
The report says: "Delegation had serious implications for free-meal provision. Pre-delegation, central contracts ensured conformity of meal prices within LEAs.
"With delegation, schools set their own prices, so that pupils using some cash cafeterias were unable to purchase an adequate meal with their free allowance.
"Pupils taking free school meals had either to subsidise the meal with personal money or select a less than adequate meal."
Funding changes in 2000 forced all councils to delegate school meal cash to secondaries. Many authorities also chose to pass on responsibility for catering to primary and special schools.
The report found that where they were given the option, most primaries wanted the LEA to keep control of meals provision.
Ashley Riley, spokesman for the Child Poverty Action Group, said: "The amount of money invested in free school meals in far too many schools is far too low. Many children from low-income families rely on the free meal as their only hot food of the day.
"It is not acceptable that in 2004, some children are still going without a nutritious meal because their family cannot afford it."
A Department for Education and Skills spokesperson said: "Governing bodies are responsible for ensuring that pupils who qualify for free school meals can have access to meals which comply with nutritional standards, and LEAs should fund schools to achieve this.
"The DfES will shortly begin monitoring nutritional standards in 80 secondary schools where the 'purchasing power' of the amount allocated to free school meals will be examined."
School meals funding delegation by Pamela Storey and Mano Candappa, institute of education is available at www.dfes.gov.ukresearch Letters 24