Headteachers in Birmingham have been criticised for diverting more than £4 million that should have been spent on school dinners.

The re-directed cash is almost equal to a quarter of the city's allocation for school meals and could be used to improve the quality of food fed to children. The controversy comes at a time of increased concern over what pupils are eating after TV chef Jamie Oliver complained as little as 37p is being spent per meal.

A city council report into childhood obesity and nutrition shows a total of £4.2 million allocated for school dinners was not spent on food in 2003/04 out of total budget of £17 million. That equates to an average of £10,144 per school or 12.9p per pupil per day.

Paul Tilsley (Lib Dem Sheldon), chairman of the authority's education scrutiny committee, said: "That money was passported to schools for meals and nutrition. I would welcome a report into this."

Birmingham education department said some of the cash may have gone on upgrading dining rooms and kitchens.

Les Lawrence (Con Northfield), Birmingham's cabinet member for education, said: "We do not have the degree of control to say a school shouldn't spend on this or shouldn't spend on that."

But Eddie Hughes, Conservative Parliamentary candidate for Hall Green, said: "The bottom line is that is money that should be spent on school dinners and that is where it should go."

The nutritional value of school dinners became an election focus after Channel 4's series Jamie's School Dinners shed light on the junk food been fed to many pupils.

Oliver was seen struggling to produce healthy meals on a budget of just 37p per pupil.

Last month the Government responded by announcing a £ 280 million package to improve school dinners including plans to increase spending per meal to at least 50p for primary pupils, rising to 60p at secondary level.

Birmingham currently misses that target, with 39p spent per meal at primaries and 57p at secondaries.

However, if the £4.2 million was re-distributed the authority could meet the criteria.

Organic food lobby group The Soil Association said: "This problem is not unique to Birmingham - all over the country school meal budgets are losing out to other school expenditure."

Education chiefs in Birmingham expressed their concerned about the poor diet of schoolchildren in a report published this week. It highlights results of an obesity study that estimates more than 12.5 per cent of five to 15-year-olds are clinically obese.

The report says: "There is a growing problem of childhood obesity and other forms of childhood nutritional issues in Birmingham."

The authority says it is committed to rolling out measures over the next two years to address the problem.

Shelia Walker, Birmingham's head of catering services, said tackling school dinners was not easy because of the size of the city.

"We are trialling new recipes, menus and experimenting with branding because we want to ensure youngsters choose the healthy things."