Jill Kirby is a writer and policy analyst, and is a former Director of the Centre for Policy Studies.

As the Tories swap clothes with Labour on their spending priorities, voters might be forgiven for wondering if there are any significant principles distinguishing the Conservatives’ campaign from that of their main rivals.

The attempt to neutralise the political salience of the NHS has drawn the Conservative leadership into pledging ever more fantastic sums of public money to this outdated and underperforming service model.  But that is surely no excuse for adopting Labour’s message – and seeking to exceed Labour’s spending commitments – on services that any sane Conservative should know are beyond the proper remit of the State.  Such as daycare for children under five, the subject of the recent Dave and Boris roadshow at Advantage Day Nursery.

At a gross cost of £750 million per annum (£350 million if projected savings can be achieved), the Conservatives have promised that current childcare provision for 3 and 4 year olds will be doubled: from 15 hours per week to 30. The money to pay for this will, apparently, be found by limiting pension tax relief for higher earners, the source of largesse which is also earmarked to pay for the promised increase in inheritance tax relief. (There must be an awful lot of higher earners needing to be discouraged from saving for their old age.)

So, why does the Prime Minister think that it would be a good idea to put pre-school children in daycare for 30 hours a week, at public expense? Because Ed Miliband has offered 25 hours, that’s why.

Does that sound too cynical? Perhaps you prefer to believe that David Cameron actually thinks six hours a day in institutions will be good for children? If he does hold such a belief, it is sadly unfounded, since there is precious little evidence to support it, and plenty to the contrary.

When Labour introduced 12.5 hours a week of free childcare for 3 and 4 year olds in 1998, 88 per cent of eligible children took up places, but the consequent improvement in their cognitive ability at age 5 was just two per cent. By the time they reached 7, that improvement had disappeared.  Would the effect have been greater had the children been kept in childcare for more hours of the day? It seems unlikely, since the largest authoritative UK study of the impact of pre-school education show that young children gain no benefit from longer hours. And research on the effect of non-parental care on the very young demonstrates negative emotional and behavioural outcomes, which rise as hours increase.

As a recent House of Lords report concludes, the Government’s drive to get more parents out to work, and their children into care, could be harming children’s development. Behind the cosy nursery images of hand painting and jigsaws lies a harsher reality of small children deprived of parental time, forced to spend the equivalent of a full school day interacting with their peer group and jostling for adult attention.

The only forms of childcare found to improve the prospects of the very young are intensive (and very expensive) programmes focused on deprived children, where social services work alongside mothers to improve their parenting. The non-targeted mass provision envisaged by the Conservatives has no hope of achieving this – it will simply act as a form of subsidy for care that, in most cases, will be less beneficial than time spent with parents.

Where a state intervention does children more harm than good, how can it be sensible to increase it?  The potential damage to children might seem reason enough to think twice, quite apart from the colossal waste of money: the government already spends an estimated £7billion a year on pre-school childcare subsidies, directly and indirectly.

Should we set aside such concerns on the grounds that it is the duty of the state to ensure that all parents are in paid work regardless of the age of their children? This utilitarian thesis might be justified on the Left, the socialist assumption being that the family is an agent of inequality and that children should be institutionalised from an early age.  George Osborne’s declared goal of full employment seems to tie in with this. But has political cross-dressing really moved the Conservatives this far Left?

There is a better solution to the “problem” of childcare, long advocated on this site.  Rather than daycare subsidies, families should be offered tax allowances to recognise the cost – and social value – of raising children whilst holding down a job. Such allowances should be based on the number of adults and dependent children living together in the family, with parents able to choose which income to set the allowances against, for maximum relief. Families providing their own childcare would then be on a level playing field with those who buy care. There would be a clear incentive for at least one parent to work, in order to claim the allowance, and it would encourage parents to live together – to the further benefit of their children – because this would enable them to pool their allowances.

Now that would be a pro-child, pro-family childcare policy, distinct from the brutal collectivism of the Left. You might even describe it as Conservative.