Why are we still debating the small change of independence?

Right now, the biggest issue in the referendum campaign is whether or not Scotland should keep the pound. Arguments about North Sea oil, the armed forces and Trident have been eclipsed by a row over whether or not Scotland could, or should, remain in monetary union with England, as the SNP wish. The former Labour Chancellor, Alistair Darling, who will be launching the anti- independence Better Together campaign on Monday, claims that Scotland would suffer "economic serfdom" if it retained sterling after independence. And anyway, he says, England wouldn't allow an independent Scotland to keep the pound.

Nonsense, say the Nationalists. Wha's to stop us keeping the bonny pound? Scotland will prosper in a new Britain as Scots and the English share a common monetary destiny. At least for the time being. Not everyone thinks this is plausible. Professor John Kay, a former member of Alex Salmond's council of economic advisers, suggested this week that Scotland might have to consider setting up its own currency, like Norway or Denmark, rather than remain under the heel of the Bank of England. Nobody seems to talk about joining the euro any more, for obvious reasons, which is unfortunate because there is an argument that, if economic and monetary union survives, Scotland could benefit from being in it.

Now, this may all sound very esoteric, and it is, but it also represents a defining moment in the Unionist campaign – the first time in at least two years that opponents of independence have actually managed to reframe the debate in their terms. Indeed, Mr Darling can be credited with coming up with what looks like a new West Lothian Question: how can Scotland be truly independent when it leaves interest rates in the hands of the Bank of England? Unionists are even suggesting that Scotland might have more autonomy within the Union than outside it, because at present we can at least influence debate in Westminster and Whitehall.

Mr Darling claims, rightly, that the crisis in the eurozone is the result of a monetary union which lacks a federal political dimension. Spain, Italy, Portugal and Ireland are being plunged into an economic depression because they lack the power either to devalue their currencies or to access direct financial transfers from richer EU countries such as Germany. We at least have the Barnett Formula. If Scotland kept the pound after independence, say Unionists, Government spending would have to be massively reduced to avoid the risk of default, just as in Greece. So much for the SNP's "social wage".

I think everyone now accepts that there was an inherent flaw in the way that the European single currency was constructed. Without a federal government and eurozone treasury, the German Bundesbank has by default assumed the role of fiscal controller and lender of last resort, much to the discomfort of the peripheral countries. But is this really analogous to Scotland's situation in the sterlingzone? It presupposes that Scotland is at an economic disadvantage in the way that Greece or Ireland are, relative to Germany. That is, that we are an economically backward country which is spending more than it earns. But this is not the case – labour productivity in Scotland is much the same as the south of England, and GDP per head is actually higher than the UK average. Scotland has considerable natural resources, such as oil and renewables. Moreover, it is leading the UK in attracting significant inward investment, as the latest Ernst and Young survey confirms.

Meanwhile, the UK is the most indebted nation on earth, according to consultants McKinsey, to the tune of 492% of GDP if you include household, corporate, government and bank debts. It could be that we are looking at the reverse of the eurozone problem: an economically rather robust small country harnessed to a UK with massive public and private sector debt which it has no way of financing in the long term and which has been keeping afloat by devaluation and quantitative easing. Not for the first time, Unionists are guilty of looking through the wrong end of the telescope – assuming that small means weak.

In this situation, being in a currency union with the UK need not imply default or sovereign debt crises – precisely the reverse. Benefiting from effectively an undervalued currency, Scotland's competitiveness could be enhanced in export markets. If Scotland had its own currency, like Iceland, it might find itself a victim of "Dutch Disease" which is what happened to the Netherlands in the 1960s when it discovered natural gas and suffered a dramatic upward revaluation of the guilder which destroyed Dutch manufacturing industry.

At the very least, as an oil economy, Scotland could benefit from the stabilising effect of a fixed exchange rate that prevents the Scottish currency leaping in value with the gyrations of the oil price. Anyway, I suspect that most people in Scotland and England would prefer to keep the same currency, if only to avoid having to exchange it before crossing the Border. I simply don't buy the argument that the Bank of England would refuse to let Scotland use the pound out of petty spite. I just don't think central banks act that way.

Of course, this doesn't alter the argument that there might be a democratic deficit leaving monetary policy in the hands of effectively a foreign country. Is a seat on the monetary policy committee of the Bank of England really enough to protect Scottish interest? Do we not want to have genuine representation and political influence, in the "federal" authority, in Whitehall and Westminster, where economic and monetary policy is framed? This is what the majority of the Scottish voters appear to want, according to the latest survey by Reform Scotland.

But it all seems a long way from national liberation. Perhaps we should regard this as a sign of maturity if emotion is replaced by economics. But it lacks, well, a certain brio. I can't imagine Wallace or Bruce worrying overmuch about the convertibility of the groat as they led the wars of independence.