Reducing uncertainty is essential if Alex Salmond is to stand any chance of winning his 2014 referendum on Scottish independence.

High on the list of uncertainties in need of resolution is the question of what currency an independent Scotland would have. Businesses need a stable currency which is not subject to excessive inflation or wild fluctuations in value against other currencies. This applies especially to exporters, but also those whose market is limited to Scotland.

John Swinney, finance secretary, has gone some way to resolving these matters by declaring in a recent interview that Scotland would retain the pound sterling for the foreseeable future and would only contemplate joining the euro when the economic conditions were right, something he could not foresee happening for some time.

This is the right policy aim. About 60 per cent of total exports from Scotland go to the rest of the UK (rUK) and only about 20 per cent to Eurozone countries. It would make no economic or business sense to adopt the euro and set up currency exchange costs for the majority of exports.

However, there is still uncertainty over whether the terms of EU membership the SNP would negotiate - and there would have to be a negotiation for Scotland to get a seat and votes at the European Council - would allow Scotland to inherit the UK's euro opt-out.

Sweden has retained the krona but is a full EU member. Although its terms of accession contain the proviso that Sweden should eventually adopt the euro, this precedent suggests Scotland could keep sterling. But it may have to do as Sweden did in 2003 and hold a referendum on joining the euro - 56 per cent of Swedes voted against it.

Assuming Scotland did get EU approval for keeping sterling, would rUK agree to that? Scotland could unilaterally adopt sterling; there is nothing illegal about using another country's currency without its say-so. But it would be more sensible for both parties if there was a negotiated agreement.

The most obvious model is to do what the Irish did with British agreement after 1922 and adopt a Scottish pound linked in value to the rUK pound. Irish banks held balances of sterling pounds equal in value to Irish punts in circulation. Everyone was happy until the Irish became worried about sterling's devaluation internationally and the European Monetary System came along, allowing them to break the link in 1979 and float the punt.

But managing a currency is more complex these days. The SNP seems content to let the Bank of England carry on managing the Scottish pound. In terms of getting agreement for that, Scotland does have a lever. If it is the case that Scotland has to take a portion of UK liabilities such as the national debt, it follows that Scotland should also get the same portion of UK assets, one of which is the Bank of England. This might yield Scotland a seat on the Monetary Policy Committee and perhaps a say in appointing one of the deputy governors.

But the big problem is fiscal discipline is vital to maintaining currency union stability and an independent Scotland will have quit the UK fiscal union. John Swinney has insisted Scotland will be fiscally disciplined. Since Greece probably said the same thing when joining the euro that assurance won't be enough.

Despite Swinney's protestations, the EU and rUK are likely to insist on scrutinising an independent Scotland's tax and borrowing plans to make sure they won't cause Greek or Irish-style instability. That also means a veto on anything they don't like.

So a lot of uncertainties remain. And as John Kay, a former member of Alex Salmond's Council of Economic Advisers, has recently noted, clearing them up might so reduce a Scottish Government's freedom of action that it is questionable whether independence is worth bothering with. ? Peter Jones is an economics journalist and co-author of Scottish Independence: A Practical Guide, published by Edinburgh University Press, 2001.