I wrote yesterday about Sir Nick Harvey’s forecast that the next election is Labour’s to lose. But there was another issue he focused on in his Huffngton Post interview – Nick Clegg’s conference pledge that all 5-7 year-olds should have free school meals, regardless of their family’s income status.

“It was absolutely astonishing. It came from nowhere,” he exclaims. “It seemed to be part of some coalition deal where it was meant to make the Lib Dems feel better about allowing the Tories to progress their wretched married couples tax allowance. I am supposed to rejoice at this other policy that seems to me to be squandering a lot of money”.

It’s not that Harvey is opposed to free school meals. Far from it. He has been campaigning on it from both within and from without government for some time. His problem is that, in a time of squeezed public spending, he wanted the free lunch to be given to poor children from when they started school at five to when they finished at 18.

Instead, Clegg decided to give the money to the youngest children while doing nothing for those who were older but poorer. The idea is to gradually roll it out to all age groups. But Harvey suspects this may take such a long time as to never happen.

“Suddenly bunny comes out of hat,” Harvey mimes. “Someone, somewhere, has found £600m a year we didn’t know about down the back of a filing cabinet and has come up with the brilliant brainwave that the best way to spend it is to give a free school meal to all five, six and seven year olds – regardless of their income level. I am sitting there, gawping in open-mouthed astonishment,” he says. …

The Lib Dem leadership’s argument is that poor children perform better in school when the entire class has free meals. Harvey says: “It’s not that I find there to be anything intrinsically wrong with providing a free school meals to all five, six and seven year olds. I am perfectly ready to believe that it is slightly more effective at closing the attainment gap. That’s perfectly plausible. But if the cost of doing that is you ignore the poor kids from eight to 18, I struggle to believe that overall this is doing more good.

“I can see it will be years and years and years before there will be any hope of getting it to secondary pupils. I think it’s a strange sense of priorities. It’s not that I’m against giving kids a free school meal, it’s just a very odd sense of priorities.”

This critique won’t be a surprise to Nick Clegg, the man who sacked Sir Nick as defence minister last year before trying to bring him back into government as the party’s chief whip two months ago. At Deputy Prime Minister’s Questions last week, Sir Nick pointedly asked:

Sir Nick Harvey (North Devon) (LD): Will my right hon. Friend explain why it is a higher priority to provide a free school meal to a six-year-old from an affluent family than to a 12-year-old living in childhood poverty?

The Deputy Prime Minister: With respect, my right hon. Friend fundamentally misunderstands the progressive nature of extending free school meals to the first three years of children at primary school. The evidence from pilots in Durham, Newham and elsewhere—I strongly urge him to visit some of those pilots—suggests that it helps many thousands of children who are in poverty but do not receive free school meals. Having children share a healthy, hot lunch every day together has a dramatic effect in closing the attainment gap in education between wealthier and not so wealthy children.

The pilots of extended free school meals Nick Clegg referred to were evaluated by research institute NatCen – which concluded that the policy improved the diet of children and improved the attainment for all children, but especially those from less affluent families.

However, it also concluded there were substantial ‘deadweight’ costs – ie, the policy subsidised parents who’d previously been paying for their children’s school meals. As Conor Ryan from The Sutton Trust notes here, “Applied to a national programme, this could mean £250m of £600m in deadweight costs.” As he adds, “that may be a price worth paying if it delivers good results” – and, as importantly, better results than could otherwise be funded with that c.£250m.

Let’s remember, one of the main arguments the Coalition used in 2010 in favour of abolishing the Educational Maintenance Allowance – the £30 a week paid to 16-18 year-olds to encourage them to stay in education – was the high deadweight costs, estimated at 88% of the total cost of £560m. The following year, the Coalitionreplaced the EMA with a more targeted (ie, cheaper) scheme, with £180m of funding allocated to schools and colleges to offer financial assistance to young people from low-income backgrounds.

Nick Clegg will argue that, in the case of universal free school lunches for infants, the deadweight costs are justified by the shared experience of all young children sitting down to eat together – and that such money is best spent as early as possible because the attainment gap between rich and poor children gets wider throughout school. For Sir Nick Harvey, though, that argument doesn’t wash – better, he says, that free school meals be targeted specifically at young people from low-income families of all ages, not just the youngest.

* Stephen Tall is Co-Editor of Liberal Democrat Voice, and editor of the 2013 publication, The Coalition and Beyond: Liberal Reforms for the Decade Ahead. He is also a Research Associate for the liberal think-tank CentreForum and writes at his own site, The Collected Stephen Tall.