Europen Union or United Kingdom. Scotland may have to choose.

   To howls of unionist derision, Alex Salmond yesterday outlined his thoughts on an independent constitution for Scotland. He holds these truths to be self evident: that Scots shall have a home as a constitutional right, that there shall be free education in perpetuity, and that there will be no nuclear weapons on Scottish soil. I don't argue with his priorities, though I can't help feeling slightly uneasy at a constitution that sounds suspiciously like election manifesto. What kind of home? Will all education be free under the constitution? Even part time and post graduate university degrees? Will my daughter's guitar lessons be refundable from the state?

There are some constitutional anomalies too. The First Minister says he is affirming the Scottish constitutional tradition of the Declaration of Arbroath, that he says was a declaration of popular sovereignty - which of course it was not. The Scottish nobles who put their seals to the letter to Pope John in 1320 weren't democrats and had no concept of the Rights of Man. But let's not quibble about that - it was a long time ago after all, and we're all democrats now. There is a more direct problem with monarchy.

The SNP's Constitution for a Free Scotland, published in 2002, says that "Executive powers are vested in the Head of State, Queen Elizabeth 11, who is expected and required to act on the advice of the Prime Minister and Ministers". A constitutional monarchy, right enough, but a monarchy nevertheless. Do we really want Elizabeth Windsor, her heirs and successors, reigning over us in perpetuity? Nor am I sure how you reconcile a pledge to reject nuclear weapons with being a member of a nuclear alliance, NATO, which hasn't ruled out the first use of them.

But least the First Minister is talking about the constitution and making positive proposals for how a written constitution might improve the governance of Scotland. The No campaign has been predictably dismissive of the whole idea - that it is Alex Salmond's ego getting in the way of political reality. "Scotland has a right to a first minister who is honest", was BT's response yesterday. The UK government has ruled out any pre-referendum talks on the transition to independence, on the grounds that they don't believe it's going to happen.

But they are missing a trick here. If they were to come up with some constitutional proposals themselves they could rebut the charge that they are only interested in negative scare-mongering. Right now, the UK government is supposed to be reforming the House of Lords, but seems to have no idea how to do it. The West Lothian Question remains an issue, and the Barnett Formula has to be reformed because the Scottish parliament is to get greater tax and borrowing powers in 2016. Better Together could run these elements together and make concrete proposals for a federal UK, with the House of Lords as a regionally-based Senate, an English Grand Committee for domestic legislation, fiscal autonomy for Scotland and a written constitution. The Coalition is supposed to be drafting a Bill of Rights as we speak, but can't decide what to put in it. There it is.

  This is a rare opportunity address not just the Scottish Question, but the London Question. Britain is becoming two nations: London and the rest of the country, and there is a pressing need for a constitution that devolves and decentralises power. But what do we get instead? A referendum on British membership of the European Union - an issue that is scandalously irrelevant to the real issues facing this country. It raises what might be called the West Strasbourg Question: what if Scotland is thrown out of Europe on the basis of English votes?

Tomorrow, David Cameron will finally unveil in a speech in the Netherlands, his plans for renegotiating Britain's relations with Europe and for a referendum on the new terms. This could plunge the UK into a prolonged political and constitutional crisis, because it is very difficult to renegotiate the terms of membership of the European Union without leaving it - which of course is what many Conservative MPs wish to see. Tory eurosceptics, like the former defence secretary Liam Fox, want Britain to have the same relations as countries like Norway, who are part of the single market, but are not part of the European Union.

We keep hearing about how Scotland will be 'thrown out of Europe' if we vote Yes in the independence referendum, but the constitutional reality is that we are just as likely to be forced to leave the European Union if Scotland remains within the UK. This makes it very difficult for Scotland to have a serious discussion about its constitutional future because we do not know what the UK's our relationship is likely to be with Brussels, which is where a lot of our social and economic legislation originates.

Now, there are eurosceptics in Scotland, who want out of Europe, but they are not very vocal. The Scottish press has been hounding Alex Salmond over the alleged threat to Scotland's continued membership if Scottish voters opt for independence. The presumption is that being in Europe is in Scotland's best interests. You do not find in Scottish public life the visceral hostility to Europe that you find in sections of the UK press and among Tory MPs. Really, to speak to them - as I have - you would think that Britain was under the heel of the Germans, that our liberties were being extinguished and our economic future destroyed.I just don't hear  these views in Scotland.

 But the uncertainty over Europe also makes it difficult to frame an independence constitution. Would Scotland be under the authority of the Bank of England or the European Central Bank, if we keep the pound as the SNP propose? And if England leaves and repatriates powers from Brussels, over human rights, working time, immigration etc., how would the "social union" with England remain?

The coming referendum on British membership could be the wild card that turns the Scottish independence question upside down. Come 2014, if it looks as if England is likely to vote to leave the European Union, Scots may find they are choosing between the EU and the UK. Scots can no longer assume that by staying in Britain they stay in Europe.