Is the Scottish National Party still a Scottish nationalist party?

It may seem a little late in the day to be asking this question, only a year or so from a referendum on independence. But it is a question that has been perplexing people on the fringes of nationalist politics for some time now, as Alex Salmond has conducted his dance of the seven tartan veils – teasing us with policies such as keeping the pound, the Queen, Nato, MI6, UK energy and pensions policy, and maybe even Morris dancing.

And even after writing a book on the subject, Road to Referendum, which is published next week along with a three-part prime-time STV documentary series of the same name, I'd have to say I am not entirely clear the SNP knows what it is about any more. Nationalists find it increasingly difficult to raise the emotional case for Scottish independence – for freedom – when they are obliged to reassure Scots continually that they will still be in the United Kingdom after voting Yes.

The prolific Scottish economists Jim and Margaret Cuthbert, who have been almost single-handedly promoting radical independence on their impressive website, have come to the uncomfortable conclusion – for them – that the SNP under Mr Salmond is selling a Unionist pig in a Nationalist poke. What kind of independence is it, they ask, when Scotland is left at the beck and call, not only of the bureaucrats of Brussels, but the beastly Bank of England? And behind it the UK Treasury, sneakily setting limits to Scottish fiscal autonomy, controlling Scotland's borrowing powers, running Scottish banks? It is not just interest rates that will continue to be set in England even if Scotland votes Yes in 2014. Much Scottish economic policy, from corporation tax to fisheries, will likely be determined outwith a nominally independent Scotland.

Some critics claim the SNP is offering the worst of both worlds: submitting to the strictures of the European single market and the CAP while staying within the confines of a UK monetary union. At least in the European Union, Scotland has nominal representation in the EU Parliament. In the continuing economic union with England, Scotland will have no democratic representation at the centre of decision-making in Westminster, because the SNP intends to withdraw all Scottish MPs. As the eurozone crisis has shown, monetary union without political representation is likely to be uncomfortable at the sharp end.

Of course, the SNP argues that, by taking over all tax-raising powers an independent Scotland will gain a great deal more political autonomy than it has at present with less than 10% of revenues raised by Holyrood. This is undoubtedly true. But it is all very well having economic powers if you can't use them. Europe is rapidly moving towards deeper economic integration within the eurozone to prevent any recurrence of the sovereign debt crisis. This will involve greater controls being placed on national budgets.

It is impossible to know at this stage what impact this will have on an independent Scotland, because we don't know whether Scotland will still be in Europe. By hitching Scotland's fortunes to the UK after independence, foregoing the option of full economic autonomy, an independent Scotland could find it is forced to leave the EU if England votes for splendid isolation in its referendum. Scotland could be left an anomalous adjunct to a crippled UK which is drowning in debt, isolated from European markets and increasingly intolerant of Scotland's autonomy.

There is, of course, a powerful argument that true independence has become an anachronism in the era of globalisation and multinational entities such as the European Union, which aren't states but exercise sovereignty over member countries. Europe is increasingly dominated by unelected multinational bodies such as the Troika – the collective noun for the International Monetary Fund, the European Central Bank and the European Union – which has been sponsoring the devastating deflationary policies that are wrecking the eurozone.

Global firms like Apple can thumb their noses at the great US Congress, so how is Scotland going to take them on? Is it realistic to believe any country can be truly independent any more, except in the reactionary fantasy world of the UK Independence Party. It could be there is no longer a national option either for the UK or for Scotland: that the best we can do is try to strengthen democratic oversight at all levels, from the global to the local.

This speculation doesn't make it any easier for Scots to know how to vote in September 2014. We know Scots want a Parliament with more powers, and they don't particularly want to leave the UK to get it. But this is the one option that is not on the ballot paper. The No option looks like an invitation for London to pay even less attention to the Scottish question than it does now. But Yes looks like a vote for an illusory independence that even the SNP doesn't really believe in any more.

The SNP is presumably hoping to invite Scots to vote for independence as a way of achieving further devolution. That is if they still hope for a Yes victory. There has been a listless quality to the SNP's prosecution of the independence case recently, almost as if the party has already discounted the referendum and is looking to position itself for the 2016 Scottish parliamentary elections. Tory politicians, economists, ex-civil servants, even accountants have been walking all over the SNP for months now, without the party seemingly able to mount any effective challenge.

The Nationalist argument is turning, almost imperceptibly, from the positive to the negative. We are hearing more about the dangers of what might happen after a No vote. First to go will be the promises of more powers for Holyrood, being offered by the Unionist parties currently. Indeed, Holyrood's powers will likely go into reverse.

If Labour and the Liberal Democrats get back to power in Holyrood they will restore student fees, increase council tax, abolish free personal care for the elderly and turn the Scottish Parliament into a patronage vehicle for the promotion of Labour's public sector cadres.

Not only will the UK Government continue to keep oil revenues, it will axe the Barnett Formula and impose an inflexible version of Calman-style tax-sharing that will erode Scotland's funding advantage. The media will become even more concentrated in London as the Scottish press declines and the BBC broadcasts endless stories on English curriculum reforms and foundation hospitals.

I think these are real possibilities, and will give Scots polling booth anxiety in September 2014. But will voting Yes to an uncertain and half-hearted prospectus ensure the gains of devolution will be secured and advanced? Will independence turn out to be another form of economic subordination, in which Scotland loses even the minimal political influence it has in Westminster, while not even preventing Scotland leaving the EU? It is time for the Nationalists to speak up – if there still are any in the SNP.

Iain Macwhirter's Road to Referendum is published on June 5 by Cargo Books (£13.99), the day after the first episode of the major documentary series airs on STV. To buy a copy, click here.