A meals-on-wheels style lunch service is being used to feed youngsters at 27 of South Gloucestershire and North Somerset's primary schools.

The lack of proper kitchen facilities means food has to be transported in to eight schools in South Gloucestershire schools and 19 in North Somerset.

It comes as tougher nutrient standards were made mandatory in secondary schools, and two pilot schemes to provide all primary school children with free, healthy lunches every day throughout the school year were launched in East London and County Durham.

The two-year trials will be evaluated, which could lead to them being rolled out to other areas in the future.

But the Tories said their survey of local authorities under the Freedom of Information Act cast doubt the possibility of extending free school meals to all primary school children.

Across the country, they discovered, three in 10 primaries do not have full kitchens, with 19 per cent transporting food from another school and some 670 schools (4.5 per cent) serving only cold food.

Shadow schools minister Nick Gibb said: "The idea that the Government will be able to find the extra £1 billion a year that it's estimated would be needed to pay for such a scheme to go nationwide is completely unrealistic in the current economic climate.

"£1bn is the equivalent of 33,000 full time teachers, they would effectively have to stop all teacher recruitment in order to pay for it, regardless of the fact that one in five primary schools don't even currently have a kitchen."

But a spokesman for North Somerset council said: "All our schools in North Somerset have access to hot meals. Where schools don't have their own facilities food is brought in.

"We applied for and were awarded £2m in government funding to improve our delivery of hot food.

"Examples of where we have made improvements include a new kitchen at Christ Church C of E primary in Weston-super-Mare, and a £750,000 scheme to build a new dining hall and kitchen at St Nicholas Chantry School in Clevedon."

A spokeswoman for South Gloucestershire Council said: "Our school meals have won numerous awards and have been praised by Jamie Oliver. Even the schools which do not currently benefit from a 'live' kitchen still have a full service which provide hot and healthy meals.

"To build on these existing high standards, we are continuing to increase both the number and quality of school kitchens. We are currently looking at ways to incorporate a full-production kitchen into all our primary schools."

No information was available for Bristol or Bath and North East Somerset.