Mark Littlewood, director of the Institute of Economic Affairs

Let's start with the obvious. Lunch, I hope we can agree, is basically a good thing. Nutritional, uplifting, convivial, educational lunches are even better. And having young kids enjoying these sort of lunches would be simply marvellous. So far, so good.

Sadly, the new government policy of spending £600m a year for "free" school meals for infants is yet another attempt to ensure that state bureaucrats assume the role of parents. I anticipate that – in aggregate – these bur eaucrats will take on this task with enthusiasm, determination, extreme confidence and horrific inefficiency. Additionally, some of these bureaucrats will get richer as they do so. It is not the job of the government to provide lunch for every child aged five, six or seven. For all but the poorest and most disadvantaged, this is a responsibility of parents.

At the cost of £10 for every single man, woman and child in Britain every year, the Lib Dems have decided to contract out the dietary needs of our young children to the likes of the Local Authority Caterers Association, with the enthusiastic endorsement of lobbyists such as the Child Poverty Action Group.

This is not a serious effort to reduce hardship. If it was, the children of millionaires would not get their lunch paid for by the hard-pressed taxpayer. This is just another gimmicky policy shifting power away from ordinary people and into the hands of the state.

Carmel McConnell, founder of Magic Breakfasts

Nick Clegg's free school lunch announcement for five- to seven-year-olds is very good news, and based on sound evidence from free school meal pilots as well as a decade of campaigning from a wide cross-section of the school food community. The most recent push for this came from the School Food Plan, commissioned by Michael Gove and published by the Department for Education. It has strong endorsement from the Lib Dems, as we've seen this week, as well as Labour.

Universal free school meal policy has both a business case and a moral case, and it makes sense whether you see it from the perspective of the child, parent, teacher or taxpayers/society as a whole. Leaving aside the moral case – which I think we all get – giving a free, healthy, hot lunch to all children will improve the health and education outcomes of a whole generation. In Newham and Durham, two of the free school meal pilot sites, students in the pilot areas were on average two months ahead of their peers elsewhere. Yes, improvements were seen to be stronger in children from economically disadvantaged families, but does that matter? We know that only 1% of packed lunches meet the nutritional levels of the average hot school lunch, so, if we want across-the-board educational and health outcomes, free school lunches is an absolute no-brainer. I'd argue the case to extend it across all primary school children and offer universal free school breakfasts as well, in schools where children arrive too hungry to learn.

ML I don't think we should "leave aside" the moral case. I don't think we all "get it". I certainly don't. What is moral about demanding that a childless person on the minimum wage pays taxes towards feeding the children of millionaires?

For me, the moral case starts with two assumptions. The first is that parents should pay for the food consumed by their own children. This is, of course, a rebuttable assumption. There are already provisions in place to ensure poorer families are given assistance.

The second assumption is that parents – not school bureaucrats – should be given responsibility for children's diets. I have no doubt there is a plethora of "experts" who feel quite certain they know what's best and that responsibility should be stripped from parents and given to them. Again, there may be extreme cases where the state needs to out-trump parental discretion, but school lunches is simply not one of them.

If there is a business case to be made – and I'm rather sceptical about this –, then make that business case to the parents. The overwhelming majority of them care passionately about their children's health and education. If you are a provider of hot school meals and can show that 99% of parents who supply packed lunches to their kids would be much better advised to purchase your offering instead, then go out and persuade them. You need to run a decent marketing campaign. You certainly don't warrant a £600m slug of taxpayers' cash to supply your product to a captive audience.

CM You started by saying that a good lunch enjoyed in convivial surroundings is a good thing, so the moral case is simply that, in order for children to do well, they need to eat well. We start the moral argument from different places. There are 400,000 children eligible for free school meals who have not registered due in some part to the difficulties of getting through the bureaucratic and somewhat demeaning system of proving low income. The universal free school lunch provision does away with that injustice, as well as the tons of time and money-sapping effort in schools and local authorities to administer the system. And, with the chair of the nutrition committee at the Royal College of Paediatrics and Child Health, Dr Colin Michie, pointing out that there are 10,000 children hospitalised with malnutrition right now in this country, and increasing numbers of children needing food-bank support, I had hoped that the moral case for good food in schools did not need to be underlined.

I understand what you're saying about not providing subsidy to the children of millionaires, of course. One of the teachers in the pilot studies pointed out that richer children are not charged for drama, or gym, even though their parents could pay more. How far do we rebut universality? Should I say that women should pay less tax towards prisons given that most prisoners are men? Should we ask for salary slips at the GP?

You are right, too, to emphasise the importance of parental responsibility. However, if a parent is not able to provide what is best for their child, either through poverty or lack of food skills or lack of time, then what do we do? Ignore the child's needs, perhaps? Let their young minds grasp at an hour of mathematics fuelled by a packed lunch consisting of a swiss roll or yesterday's leftovers? Schools that have taken part in one of the universal free school lunch pilots reported improved child concentration and behaviour in school. Grades went up. Children ate more vegetables. If we believe in education, don't we also want to make sure our children make the most of their school time? Isn't investing in learning a good idea?

Now, to packed lunches. This is not about the "state out-trumping parents" facing tough facts. Parents currently spend almost £1bn on packed lunches, but only 1% of them meet nutritional standards. And separating out packed-lunch children and hot-school-meal children is simply a pain for most schools. Read the School Food Plan for much more on this.

As a taxpayer I am very happy to know we'll make the most of our education system by giving more children a free hot lunch. Schools are where children learn. This new provision will, I hope, boost long-term health by helping children gain an early love of good food, to try new foods and enjoy doing so with their friends. It is a great investment.

ML Well, we may need to differ on what constitutes a "moral case". There are many things in the world that are nice and desirable; this doesn't amount to a moral case that the government should provide them, though.

In terms of universality, I think we need to move away from it. Overall government spending on welfare is way too high: the obligation on the state should be to spend less but spend where it is most needed. If the present system is bureaucratic and demeaning, reform the present system – don't widen it.

At best, you are making a case that school lunches should be compulsory, but that is not the same as the taxpayer footing the bill.

I think you give away the game in your last point, though, that the present arrangements of children having different eating habits is not "convenient" for schools. Too often these days, policies seemed designed around the desires and needs of public sector workers, not the choices of the people they are employed to serve.

CM I'm not playing a game: I'm passionate about all children getting the chance to do well at school, and right now too many miss out on the full classroom experience because they are hungry or malnourished.

For one in four children the only hot meal they receive is the meal provided at school. And the flip side of poor nutrition is obesity – an incredible 20% of children at reception stage. If we make sure more children get a hot, healthy meal at lunchtime (and breakfast, you'll have gathered I'm keen on that), we will reduce the £6bn we spend each year on diet-related illnesses. We've also got about half a million people in this country who earn just above the eligibility threshold for free school meals. This announcement eases their financial burden. That has to be a good thing, doesn't it?

This is a massive boost to young children at a time in their lives when they'll really benefit from it. A healthy hot lunch improves a child's chance to learn and succeed; for the taxpayer, it delivers multiple social benefits. And, if you'd like to visit any one of these successful, food-loving schools to see for yourself, you'd be my very welcome guest.