Campaigners have raised concerns that school dinners are at risk after the Government failed to introduce rules for proper kitchens and canteens.
They said they are disappointed that new school premises regulations, introduced this year, have been watered down and do not clearly state a requirement for schools to have adequate facilities to provide meals for pupils.
Children are more likely to choose school lunches if they are cooked from scratch, according to the Children's Food Trust.
The previous regulations, which date to 1999, said that schools must provide buildings which "allow for the preparation or serving of food and drinks and the washing of crockery and other utensils", and should also consider providing "adequate facilities" such as cold storage for food that pupils bring to school.
The new premises rules do not contain these details.
Instead, campaigners say that the section which can be related to school food simply says: "School premises and the accommodation and facilities provided therein must be maintained to a standard such that, so far as is reasonably practicable, the health, safety and welfare of pupils are ensured."
Anne Bull, national chair designate of Laca (Local Authority Caterers Association) said: "Laca is disappointed to see that the new School Premises (England) Regulations 2012 do not clearly state the requirement for schools to provide adequate facilities for the preparation or serving of food and drinks for pupils, as had been the case within the previous Standards for School Premises (1999).
"As part of the Government's targets for reducing obesity levels and its aim to improve children's health through better diets and lifestyles, school meal providers are expected to prepare nutritious meals from fresh ingredients. Not having kitchen and dining facilities clearly specified within the new school premises regulations shows a worrying contradiction in policy."
Complying with nutritional standards of school food is compulsory for all local authority-run schools, Ms Bull said.
Under these standards, schools and caterers are required to provide a daily hot meal for pupils, as well as free school meals for those that are eligible.
"It would be impossible for them to comply with the law without appropriate kitchen and dining facilities being retained by headteachers and also included in the planning for new school builds."
A Children's Food Trust (CFT) spokesman said: "We know from our research that in places where more schools have the facilities to cook from scratch, more children tend to take up school meals. And young people themselves tell us that where they eat is actually more important to them than what they eat.
"So if we want more pupils to be eating well during the school day, we need to support good kitchens and dining areas."
In their response to a consultation on the new regulations, the CFT called for the 1999 guidance to be kept, and expanded to include dining areas.
"If schools want pupils to be fit to learn, with an understanding of what it means to eat well, they need efficient kitchens, cooking fresh, healthy meals, and attractive dining areas where children want to spend their lunchtime," it said.
In many schools, kitchens are outdated and poorly designed, it said, adding "in our view, the removal of these regulations could directly lead to the degradation of the school food service".
The concerns come just a week after ministers revealed new templates for new school buildings which will be up to 15% smaller than those built under the last government.
Under the plans, the size of corridors, halls and canteens are reduced, as part of an attempt to help keep down the costs of creating school buildings.
The size of a secondary school will be cut by up to 15% and a primary will be cut by up to 5%.