Scotland and the NHS: Fears stoked in England gain popular appeal north of the border

The NHS is one of the best examples of how devolution has allowed the institutions of the UK's four nations to diverge.

It operates independently in each country and, as Gordon Brown has challenged Alex Salmond make clear, its budget for Scotland is set by Holyrood - albeit paid for out of the block grant that comes from Westminster for all public services.

Even so, the health service's future is such an emotive issue with voters it is no surprise that it's once again at the heart of the referendum debate.

Threats to to the NHS anger people, a fact the Yes campaign has capitalised on with their assertions that Westminster's "cuts agenda" and the "privatisation" of England's health service will force Scotland to reduce what it spends on health.

Let's look at the "cuts agenda" first. In fact, England's NHS has been largely protected from austerity cuts, its budget "ringfenced".

Of course it's still experiencing it's most painful ever financial squeeze and there's a yawning gap between demand for healthcare and funding available.

Read: Yes campaign faces scrutiny over NHS spending claims

But relative to other public services, it's been looked after. Today's analysis by the Institute for Fiscal Studies spells out how Scotland has chosen to fund its NHS by comparison, figures which I've examined in another blog.

Could an independent Scotland give the NHS better protection? That ultimately depends on how much money the new country will have, and how capable it would be of reversing the UK coalition's austerity measures. And that's an argument which ranges far beyond healthcare and into oil revenues and national debt. So I'll move on.

What about the threat that English "privatisation" poses to Scotland's NHS budget, then?

The problem here is the vagueness of the term "privatisation". It is true that private firms are increasingly being used to provide services in England, but the money to pay them still comes from the public purse.

It is privately provided, but not privately paid for. So there is absolutely no impact at all on the size of the block grant that Scotland gets for public expenditure.

The kind of privatisation that would have an impact on Scotland's budget hasn't actually happened. NHS spending in England would only substantially drop off if citizens switch to private health plans in huge numbers, or if the government brought in charging for treatment, or if a health insurance system were introduced.

None of that's on the horizon, but it is a scenario the Labour Party has painted as likely to happen under the Tories. So the fears Labour has stoked about the English NHS have been appropriated by the SNP and used to attract Labour supporters to the Yes campaign.

Will the furious rearguard action now being fought by the No campaign, with Gordon Brown at its head, swing opinions back again? We'll have to see.