Prue Leith is hunting through the cupboards in her pristine white kitchen for her coffee, without success. "I had caterers in for a dinner party last night and they must have put it away in the wrong place," she says apologetically. Entertaining, eating and enjoying food is a round-the-clock affair for Leith, a self-made millionaire from a successful 30-year career in the food and catering business, the author of a dozen cookery books and now in her newest role as chair of the School Food Trust, the independent body set up to help the government improve school meals.

In her 66 years, she has never eaten a Turkey Twizzler or a chicken nugget, she admits. But she recalls "the ghastly experience" of once eating a McDonald's, when on the way to a board meeting. "I was so hungry. I asked the driver if he could stop and buy me a sandwich, but he said there was only a McDonald's. I bought a Double Mac [sic]. I thought at first 'What is all the fuss about?' But after that I wondered what the hell I was eating. Never again."

Leith started her three-year, £15,000-a-year, part-time post last month, and although she is only supposed to do 30 days a year, she says: "I think I've done 30 days already. I did a lot before I arrived."

Ignorance about food

She is clearly enjoying her new role: "I've been banging on about school meals for goodness knows how many years but at least now people at the DfES are listening. I think that allowing the nation to become so ignorant about food has been such a backward step - and to be honest I don't think there should be a School Food Trust. It shouldn't be necessary. If we didn't have this 25 years of degradation of school meals and knowledge of food and the public getting food ready-made from a shop instead of understanding what is in it, we wouldn't need to exist. It is a terrible indictment of politics today that we are in this situation." She also blames the removal of practical cookery lessons from the school curriculum.

Asked about the slump in the take-up of school meals since the government introduced higher nutritional standards, she says the speed of change - triggered by the mood of the nation after Jamie Oliver's high-profile TV campaign - was such that schools were just not prepared. "The truth is that schools hadn't prepared the parents or the children for the changes. Children aren't being taught to cook or encouraged to try things or told why food is important. Jamie captured the mood of the nation, so the trick was - absolutely rightly - to act quickly." The trust is in the process of producing figures on uptake of school meals that will be critical to determining whether it meets challenging targets to reverse the trend.

The Soil Association's well-known "dinner lady", Jeanette Orrey, told Leith that after one school cook had done a two-day training course at the Ashlands organic "dinner lady school" in Essex, the uptake of school meals at her primary school soared from 30 youngsters to 180 within just two weeks. Leith's own experience running successful restaurants and catering companies makes her conscious of the financial bottom line, which is a key issue for schools and local authorities. "If a caterer doubles the number of meals children are eating, it makes such a difference to their profits - they would be more enthusiastic and do more things. A small increase might make the difference between losing money and breaking even, which is extremely important. But it is the big increase that will make a difference."

Creating a better-qualified, motivated and respected workforce through a major training programme is at the forefront of the trust's work and on Thursday Leith will welcome school cooks and their headteachers from every region in the UK who have already completed their training, who will then head to Clarence House for a thank you from the Prince of Wales.

Getting headteachers "on side" is critical, Leith says. "You can't tell headteachers what to do, how to run their schools. We have to get them on board. We have lots of conferences and workshops planned."

Currently exercising her is the "mammoth task" of finalising the regulations governing the new nutritional standards for school meals: "There is quite a bit of tinkering to be done. For example, the body that preceded the trust specified that pre-formed meat products - they had chicken nuggets and burgers in mind - shouldn't be served up as school dinners. But the problem was that also scooped up healthy food such as home-made sausages. So we've got to change that."

There are other pressures, not least from the food industry itself. "There's a lot of good practice, but on the other hand there is also every single lobby group and manufacturer, who have all got a legitimate interest."

The power of business

Despite her business background, she is not afraid to spell out her fears about the power of big business: "The obesity problem among children is very serious. When advertising budgets are big and business can corrupt the way we live so that it becomes the norm to snack all day - and if you are never hungry you are never going to feel like eating a healthy meal - that can't be right."

At times Leith emphasises that her personal views on some areas are not the same as those of the trust. She doesn't think much of the idea, mooted in the previous few days by the schools and children's minister, Parmjit Dhanda, for example, that schools should install plasma TVs in their dining rooms in order to encourage more children to eat school meals. "I wouldn't encourage schools to spend money on expensive plasma screens. I want children to talk to each other when they have lunch."

The trust is looking at a series of incentives to encourage school meal take-up, which include loyalty scratch cards - possibly combined with a "smart card" for payment that would reward them for high take-up, even giving them the chance to win items of equipment for their school.

Getting to parents is a further challenge, given that only 17% of food is consumed at school (some of it in packed lunches). "I do think it is the responsibility of parents to feed their children properly. They wouldn't put their children in a pair of shoes that were too tight. Putting bad food into children is much worse because it is ruining their life chances."

Leith thinks the cost of a school dinner - an average £1.50 - is "too tight" and should be raised to £1.80 to allow the use of more varied ingredients. But many families would struggle to afford that and she would like to see the education department revise the free school meals rules to allow more to benefit.

Finally, she says she is prepared to give ministers "a good kicking" if they fail to match their promises. "What is the point of independence if you can't be independent? They'll give me a good kicking if I don't do the job, so there could be a lot of mutual kicking going on."