The Education Secretary said that crisps, chocolate and fizzy drinks would be banned from sale in schools from September 2006. Schools will be required by law to empty vending machines of the products and remove them from tuck shops.

A spokesman for Ms Kelly said that new legislation would cover “any way that food is served in schools, in tuck shops and vending machines”.

Processed burgers, sausages and other foods high in fat, salt and sugar content will also be outlawed as part of new nutritional standards for school canteens. Ms Kelly told delegates at the Labour Party conference in Brighton that it was time to act against the diet of junk food served to pupils at school.

“I am absolutely clear: the scandal of junk food served every day in school canteens must end,” she said. “And because children need healthy options throughout the day, from next September no school will be able to have vending machines selling crisps, chocolates and sugary fizzy drinks.”

Head teachers’ leaders said that many parents send children to school with packed lunches containing crisps, chocolate and fizzy drinks. They also said that head teachers could not change what was sold in vending machines because they were controlled by outside contractors under the Government’s Private Finance Initiative.

Ms Kelly’s spokesman said that companies would have to amend their contracts to comply with the new law. Instead of sweets and crisps, vending machines will be expected to offer items such as milk, bottled water and fresh fruit.

The Education Secretary said that she would publish a report next week by the Government’s school meals review panel setting out detailed proposals for tough nutritional standards.

Her announcement followed government promises to improve school dinners after a television campaign by the celebrity chef Jamie Oliver highlighted appalling standards of nutrition.

John Dunford, general secretary of the Secondary Heads Association, said that a ban on unhealthy food in schools would be difficult to implement. “Children eat over a thousand meals a year, but less than 200 of these are in school,” he said. Mr Dunford said that plans to make Ofsted responsible for inspecting the quality of school meals was “just silly”.

Mick Brookes, general secretary of the National Association of Head Teachers, said: “School leaders are heartily sick of having initiative after initiative foisted upon them.

“We wholeheartedly support healthy schools programmes, but to expect schools to provide a quality meal for less than the price of the cheapest unhealthy burger does not stand up to serious scrutiny.”

Margaret Morrissey, spokeswoman for the National Confederation of Parent Teacher Associations, said: “What we would like to hear is that every school in the country has to provide a hot meal for children.”

• In her speech, Ms Kelly highlighted St Bartholomew’s Primary School in Brighton as a model of what Labour had achieved in education after eight years in government.

  She told delegates that she had visited a breakfast club at the 180-pupil school, where almost half the pupils are on free school meals and a third have special educational needs.

  “Conference, eight years ago, children at so many schools like St Bartholomew’s were written off. Their school buildings were crumbling; standards were poor; morale was low; teachers in short supply,” she said. However, national curriculum results for 11-year-olds at the school were lower in English, mathematics and science this year than they were in 1997.

  Fifty per cent of pupils achieved the expected standards in English and science, and 45 per cent in maths. In 1997, 64 per cent reached the standard in English, 75 per cent in maths, and 79 per cent in science.

  Amanda Healey, the head teacher since 1997, who said the school had benefited from many government initiatives, added: “Our results vary from year to year depending on the cohort of children.”

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