Discussion about childcare was absent from last week's televised Referendum debate.

A key issue for many families, it might have formed part of the debate on how public spending can be maintained as the working age population decreases. So what questions should be asked of the two campaigns?

All of the political parties broadly recognise the importance of Early Learning and Childcare, known internationally as Early Childhood Education and Care (ECEC). But this is an issue that not only demonstrates their different approaches to public welfare but also illustrates the problems posed for the Unionist parties by the split responsibilities for ECEC at Scottish and UK levels of government.

Holyrood legislates on the supply of early education and family services but Westminster is responsible for the tax credits and benefits used to boost demand for services.

On offer from the SNP is a high quality ECEC system for all children from the age of one to when they start school, through a progressive extension of the entitlement to free early learning and childcare. By the end of the second Parliament, this would give three and four-year-olds and "vulnerable" two-year-olds access to the same number of hours as primary school children.

It is argued that this approach is only possible through independence, as it requires investing directly in services rather than subsidising demand, with funding following the child through the tax and social security system. Its sustainability is linked to its simplified structure and, crucially, tax revenues resulting from increased labour market participation and job creation, as well as benefit savings from an associated reduction in poverty. After independence these would accrue to Holyrood.

The argument for these proposals is supported by international evidence on the advantages of universal integrated ECEC systems. While some questions have been raised over detail around the initial costings, there can be little doubt it is a cost-effective model. Questions might be asked about what the White Paper does not contain, particularly the absence of any mention of school-age childcare and, more generally, the role of schools. Giving pre-school children access to hours equivalent to primary school highlights one of the problems confronting parents at present: the mismatch between their hours and those of schools.

To those urging us to vote No, we need to ask what lessons have been learned from the UK/Scottish split in ECEC responsibilities. We need to know whether the proposed additional tax and social security powers would include childcare tax credits and benefits and, over time, enable the transfer of this resource to direct funding of services and allow tax revenues to be recouped.

Would a federal UK, proposed by the Scottish Liberal Democrats, make a difference? Its decentralised approach has much to commend it and Canada's federal structure has not prevented Quebec from developing a distinctive ECEC system, notable for having reduced inequalities of access. But the LibDem proposal, adopted nationally, reserves welfare to the UK as a whole. Moreover, the experience of Quebec suggests that federal governments like to reach out to the people directly through programmes and tax benefits of their own.

This would matter less if the UK system did not involve a mixture of demand and supply funding, and if there were shared aspirations across the UK for delivering ECEC. The best hope of achieving this might be through working at EU level, as the Scottish Government is doing, in using the 2011 Communication on Early Childhood Education and Care to address integration and quality. At the same time, the UK has discouraged a legislative approach similar to that used for maternity and parental leave to develop entitlements to ECEC services.

So closing questions to both campaigns might be: will they support a stronger ECEC framework at EU level? And where does a more substantial role for EU social policy feature in the discussion over Scotland - and the UK's - EU membership?