In fairness, the Scottish Government's paper on the economic case for independence is not intended as a policy document.

So, apart from restating the SNP's well-ventilated arguments for cutting Corporation Tax and air passenger duty (APD), it gives little idea of what an independent Scotland would mean for taxpayers. Rather, it is intended to create an atmosphere of confidence around the idea of "Scotland's future in Scotland's hands".

The central contention is that Scotland has a number of key economic strengths and all the ingredients needed to become a successful independent country. Few on either side of the independence debate challenge the idea that Scotland could go it alone but to win in September 2014 Alex Salmond needs to show that Scots and Scotland would clearly benefit from cutting ties to Westminster.

Loading article content

Much of this paper is historical, arguing that Scotland's naturally strong economy has been hamstrung by successive UK governments and Scotland is in a stronger fiscal position than the UK as a whole. Mr Salmond is right to argue that the failure to use the bonanza of North Sea oil to set up a Norwegian-style oil fund for the benefit of future generations was a missed opportunity. But in criticising the last two UK governments for slashing capital spending, he is on less safe ground. In the wake of the 2008 banking crash, austerity was on the menu all round the western world and there is no reason to believe an independent Scotland could have escaped without cuts.

On APD, it is hard to square a Government that aspires to global leadership in the low carbon revolution with policies to stimulate air travel. As for Corporation Tax, the UK is already on track for a 20% rate by 2015, one of the lowest rates in the world and the same rate modelled by the SNP. It is hard to see how a race to the bottom on this between different parts of the UK would benefit any of the parties involved.

The strengths of Scotland's economy can be used on either side of the argument. Scotland's continuing strong performance in oil and gas, for example, depends partly on UK taxpayers underwriting major decommissioning costs, while investment in renewables relies on the contributions from customers' energy bills throughout Britain. Yesterday Mr Salmond suggested an independent Scotland would refuse to shoulder its share of the national debt if it was unable to remain in the sterling zone. A currency union is, as the First Minister argues, the most likely outcome but on what terms? He concedes the Bank of England would retain some control over Scotland's debt and borrowing. What about fiscal policy? Is it likely the UK Treasury and Threadneedle Street would stand back and allow a Scottish Government to introduce a tax framework designed to lure businesses across the Border? The report also ignores the issue of occupational pensions.

This may represent the future according to Mr Salmond but it leaves vague much of the detail of what an independent Scotland would look like.