Parents will also be issued with guidelines on food high in fat and sugar which should not be included in their children’s packed lunches.

Nuts, seeds and yoghurt drinks will replace crisps, chocolate and fizzy drinks in tuck shops, after-school clubs and vending machines, say the draft guidelines issued yesterday by the government-appointed School Food Trust (SFT).

The laws to wean children off sweets and chocolate will be among the toughest in the world and will take fizzy sugary drinks off the menu, as well as diet and sport drinks and flavoured waters.They come just days after the Audit Commission attacked the Government for its indecision and lack of leadership over the implementation of measures to curb child obesity.

Children will be allowed to have milk, yoghurt drinks, water and fruit juices as well as tea, coffee and low-calorie hot chocolate. Crisps will be banned at all times, but cakes and biscuits will be allowed at lunch and in after-school clubs.

Dame Suzi Leather, chairman of the SFT, said the rules, to be introduced from September, were necessary because children were eating too much sugar, fat and salt with “little or no nutritional value”.

“They [the new rules] cannot succeed if pupils are surrounded with chocolate, crisps and drinks that fill them up with sugar and fat during the school day,” she said. “Anecdotal evidence suggests that when these products are removed, behaviour improves and this could also have implications for better learning.”

The SFT said that about a quarter of children were obese or overweight and 53 per cent of the 4-18 age group had dental decay.

The food and soft drinks industry is estimated to make £45 million a year from school vending machines. Schools are believed to make £2,500 a year per vending machine.

A spokesman for the Automatic Vending Association, whose machines are only in secondary schools, said: “We think educated choice would have been better than outright prohibition.”

Masterfoods, which supplies Mars and Snickers bars, said it was “disappointed with the SFT’s simplistic approach. Banning certain foodstuffs will not work. Young people need to understand how to enjoy a balanced diet and active lifestyle.”

Dame Suzi said that the SFT would also be strengthening lunchbox guidelines, and would expect schools to advise parents of what should be included in a healthy diet. The SFT guidance is out for consultation until May.

The Education and Inspections Bill, which was published this week, requires governing bodies and local authorities to comply with healthy eating regulations in the provision of “all food and drink provided on the premises” of state schools. It gives ministers power to ban specific types of food and drink from schools and states that the rules will apply “to food or drink provided by contractors under arrangements made with LEAs or governing bodies”.

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