The school meals tsar Prue Leith admits today that she has just three years to convince Britain's seven million schoolchildren to adopt healthy eating habits.

Otherwise, she fears that people will "lose faith" in the campaign to improve school meals.

If that happens, nutritional standards in school dinners could slip back to the level of neglect that has dogged the service for the past two decades.

The food writer and cookery expert, appointed by the Prime Minister to chair his newly-created School Food Trust, spoke to The Independent as thousands of school dinner ladies prepared to spend the half-term holiday training in the skills needed to deliver the Government's new nutritional standards .

The School Food Trust - which is responsible for introducing healthy eating standards in schools - is organising nine regional conferences for school dinner ladies this week, backed by a £15million grant.

Celebrity chiefs - including Jamie Oliver, whose Channel 4 TV programme on the state of school dinners spurred the Government into action, and the Ready Steady Cook chef Lesley Waters - will provide tips and support to help them succeed in winning the next generation's hearts and minds for a healthy eating lifestyle.

Early indications - stemming from a survey by the BBC - show a falling off of 5.8 per cent in the take up of school meals since the campaign was launched.

However, Ms Leith said: "We need a much bigger survey before we really know what's going on. I am told that the fall-out is very common and a not unexpected blip when you start to do something that's new.

"I think that's our biggest worry, though, if people start to lose the faith. At the moment, we've got huge goodwill going for us with the media and the Government on our side. I think we've got two or three years to make it, or otherwise, interest will turn elsewhere."

Ms Leith spoke of the "criminal neglect" which the school meals service had suffered over the past 25 years.

She confessed that the campaign had used "shock and awe" tactics to turn eating habits around - banning items such as fizzy drinks and chocolate from school vending machines from the start of this month and bringing back minimum nutritional standards for dinners.

"I confess that - in my own mind - I'm not a great supporter of too much nanny state and government intervention," she said, "but sometimes, children need a nanny."

She said she felt school dinner staff had been neglected over the years - and that younger recruits had not been taught to cook but "merely open packets".

"Their service was just seen as a tremendous nuisance by headteachers because it cost money. They were cooking in grotty kitchens and serving meals in terrible dining rooms.

"Now, though, we have a fantastic opportunity to improve things.We will be having quite a big discussion on the whole school approach to improving school dinners at these conferences - how healthy eating can have advantages for school behaviour and concentration in class and in tackling obesity.

"The teachers, after all, are really only interested in two things - how it will help league tables and what Ofsted will think. The answer is it can help there."

Designer decor sells more lunches

A new bistro-style dining area has increased fourfold the take-up of school dinners at Coombe Dean comprehensive school.

As they recline in leather settees, pupils aged from 11 to 18 canenjoy one of seven different recipes on offer every day.

It is all a far cry from the Dickensian dining hall conditions that still exist in too many state schools, according to school meal campaigners.

"We wanted to change the image of school meals as something you tipped down before you went out and kicked a ball about, to something of a social experience," said headteacher Pattrick Frean.

"It's had a remarkable effect - both in improving the self-confidence of the staff and in the pupils' attitudes. Napoleon was right about the importance of the army's stomach."

The changes have also allowed the 1,100-pupil school in Plymouth, Devon, to pre-empt the Government's minimum nutritional standards for school dinners.

Teachers have indicated they notice better behaviour in the classroom as more pupils are eating nutritional school meals.

And, after two years, "the designer furniture is still respected," said Mr Frean.