The coalition cut which takes food from children’s mouths

Here's the thing about efficiency savings: you never see what gets cut. If you privatise a train line and cancel the last two stops to a village somewhere, it certainly looks efficient. You slashed a significant cost. But it's not efficient for the kid who can no longer get a train home, or the shops which are forced to close up. Efficiency is in the eye of the beholder.

The same is true for child maintenance, which is currently becoming a lot more efficient – for the state, anyway. When the coalition government came in, it professed its desire to help parents deal with their financial disagreements themselves. Of course, it wasn't out of some grand libertarian principle of a concern for the autonomy of parents. It was to save money. Chasing fathers for their payments to children is an expensive and time-consuming business.

We don't know what the repercussions of this are, because it's off balance sheet. No-one is checking how many kids lost the money they would otherwise have had, or how many mothers – and they are nearly always mothers – caring for a child on their own have had to make do with less, or how many obstinate fathers – and they are nearly always fathers – have been able to get away without fulfilling their responsibilities.

The coalition is gradually replacing the Child Support Agency (CSA) with the Child Maintenance Service (CMS). Mothers receiving payments from their former partners are having the contract cancelled. They are expected to either come to a private arrangement or go through the new organisation.

Here's how it goes. Before she can even contact the CMS, the mother has to call the Child Maintenance Options service. They will encourage her to come to a private agreement. If the parents can't agree, the mother has to pay a £20 application fee. It may not sound like much, but to a person applying for financial help it may well make all the difference. It is a disincentive to claiming the money the mother and child should rightfully have.

Victims of domestic violence, by the way, aren't supposed to have to pay the £20 fee, but the women calling the agency won't be asked if they're victims. Instead, they must provide evidence they reported the abuse to a recognised charity.

According to the government's own estimates, 100,000 families will stop getting maintenance payments.

At this point the parents are still supposed to come to a private arrangement, without state involvement. This only changes if the paying parent fails to do so. If the payment is missed by over 72 hours, the mother can complain to the CMS and the 'collection service' is activated. Once it is used, they will take an extra 20% from the father and keep an additional four per cent of the payment before it reaches the mother. Over the course of a year that four per cent would average £70, equivalent to a term of school dinners. To be generous, I have tried to come up with a moral argument for this penalty of the recipient parent, but I just can't think of one. It will take a more imaginative mind than my own to justify it.

The Department of Work and Pensions predicted that the £20 fee would result in a 12% drop in the CMS' monthly intake. Recent official figures showed 2,900 fewer parents applied to the CMS in November than in May, the last month before the charge was introduced. That's a 30% drop, well over double what the government had predicted. This is only set to get wore as more and more single mums have their arrangements cancelled.

Many single mums receiving child maintenance are not well educated or aggressively self-interested. They are often unaware of what they are entitled to. The prospect of receiving a payment is often so remote to them that they'd rather just save the £20. Financially it's the wrong call, but the government is counting on mothers making it. The idea that the state stands behind single mums as a guarantor of decent treatment by the absent father is gone. They are being left on their own.

As the chief executive of single parent charity Fiona Weir said:

"At the moment, only two-fifths of the UK’s two million single parent families receive child maintenance payments from their child's other parent. We warned the government that the charge to access the new service could make this situation even worse. These early figures seem to confirm our fears.

"Children in single parent families are already twice as likely to live in poverty as those in couple families. The government should not be putting barriers in the way of the three million children growing up in single parent families getting the support they need."

The DWP expects to make £170 million per year in child maintenance fees once the system is fully operational.

We should be clear what this is: the government is taking money from children of single parents. That is the end result, but it also the intention. The DWP expects to make £170 million per year in child maintenance fees once the system is fully operational. That includes £1.4 million a year on application fees and £27 million in care collection fees. This is all money which would otherwise have gone to the children.

Between now and May 2018, 800,000 CSA cases will be closed. According to the government's own estimates, 100,000 families will stop getting maintenance payments as a result of the changes. They have so far underestimated the effect of their reforms and there is little reason to expect that to change.

But the government is not collecting any data on the women who, after calling the Child Maintenance Options helpline, decide not to apply and pay the £20 fee. Maybe they do go on to make their own private arrangement. Maybe they don't. Ministers evidently don't care or they'd bother to find out. We only count what matters to us and in this case that is the profit made by the DWP.

The single mothers who lost out by the new system are off balance sheet. It doesn't matter what happens to them. That's not the efficiency we measure.