So what would an English parliament actually look like, if those 61% of English voters, in last night's Newsnight poll, who say they want one, get their way. Well, I'm tempted to say that an English parliament would be a bit like day one of a Liberal Democrat party conference. The LibDems already have a federal structure and delegates from England sit, in splendid isolation, at their annual conference to talk about English affairs.

But it's not at all clear that the English people are ready for a full federal future. The Campaign for an English Parliament insists that an English parliament "would not require a federal system of government" to address what it calls "the festering injustice" of Scottish devolution. CEP seems to believe that the existing Westminster parliament would be fit for purpose, so long as the Scottish MPs were removed from it, and only allowed to vote on reserved matters.

Seems an attractive idea. Most English people regard Westminster as the English parliament already, with good reason. For 300 years, English MPs voted for Scottish legislation, imposing measures such as the poll tax, without anyone noticing there was any injustice.

But let's not go back over all that. We are where we are, and if there is a demand for an English parliament, then of course there should be one. That is every nation's democratic right.

Personally, I welcome any debate about how to reform and improve Britain's constitutional arrangements, provided the reforms genuinely improve democratic accountability. The debate on English devolution could spark a new constitutional settlement. It could open the way for further powers for the Scottish Parliament, a bill of rights defining our freedoms and proportional representation in Westminster. It could also, of course, lead to separation.

What it certainly will not do is restore the previous status quo where Westminster was the de facto English parliament. I'm not entirely sure that the English devolvers have quite grasped this yet. Advocates of English devolution use slogans such as "English votes for English laws" to obscure the realities of governing in a multinational state.

The essential problem is that, in a unitary parliament, it is very difficult to say what an "English vote" is. Because England, with five-sixths of the UK population, dominates the UK, any bills with financial implications affect the Scots and the Welsh profoundly. This point has been made forcibly by Lord Falconer in the Lords in March 2006.

I'm not saying that this is a reason for rejecting legitimate demands for English devolution. However, it does mean that the idea of just converting Westminster back into the English parliament won't do. You can't just arbitrarily ban Scottish MPs from certain votes - and it is most unlikely that the Speaker, whoever he or she is, would allow MPs to be removed.

And even if Scots could reasonably be excluded from English votes, you would be left with an anomaly far greater than the West Lothian Question. As Robert Hazell of the Constitution Unit puts it: "It would create two classes of MP, and lead to potentially serious instability if the UK government could not command a majority for its English business."

There might have been a slim chance of asymmetrical devolution working following Scottish devolution, because of Scotland's size relative to England. Scotland's 59 MPs are vastly outnumbered in a House of Commons of 650 and their legislative impact is pretty marginal, or "de minimis", as constitutionalists put it.

Scots MPs voted, famously, on the 2004 Higher Education Bill, which introduced top-up fees in England, but that didn't stop it becoming law. English education and health have been going down a very different road to Scotland, towards privatisation and marketisation, and this hasn't been hampered by the presence of Scottish MPs in the English lobbies.

However, this is as much an issue of perception as reality. If English people find Scottish MPs interfering in English affairs offensive, and many clearly do, then they have a right to demand that something is done about it. However, they have to be clear that this will require a radical restructuring of the UK constitution essentially along federal lines.

Here's how it might go. After a constitutional convention and a referendum had established the demand for English devolution, a joint committee of both Houses of Parliament plus the Scottish Parliament and Welsh and Northern Irish Assemblies would be set up to draft a new multinational constitution.

There would have to be new funding arrangements and equalisation formulae to ensure fairness across the new states. This would almost certainly involve new tax powers for the parliaments of the new federal UK (which we would have somehow to avoid calling the FUK).

A new elected federal level of government would have to be set up to oversee common functions of the UK, and a supreme court would be needed to adjudicate on disputes. Regions like the north-east and north-west of England would also have to have some kind of distinct representation to ensure that their voices were heard.

Curiously, the Campaign for an English Parliament is fiercely opposed to regionalism, claiming it would be "a reversion of England to the ninth century". I don't understand this since the CEP continually refers to regions such as the north-east getting a rough deal in public spending compared with Scotland. Addressing that would inevitably raise the question of public spending relativities within England.

Could all these constitutional problems be resolved without the United Kingdom fracturing? Possibly, though there must be a 50:50 chance that the effort of fixing the FUK might break it. Passions would be unleashed which might be difficult to control, especially when it came to things such as Trident, oil and Barnett.

The Campaign for an English Parliament is convinced that Scotland is robbing the English taxpayer blind. According to its website: "Each citizen of Scotland and Wales receives 28% more on public services than each taxpayer in England thanks, to the infamous Barnett formula." If this ever were the case, it is no longer.

As The Herald reported last week, the Gers figures show that Scotland's spending advantage on health and education is around 6% and 10% respectively, down from 26% and 19% in 1999. Anyway, the SNP would argue Scotland has been contributing around £12bn a year in oil revenues.

This argument rapidly could get out of control.

Scotland might then say it wanted rid of Trident and demand independent representation in Europe. That would open the way for the velvet divorce court. But here's the catch. I believe Scotland, England and Wales would soon come together again very quickly.

Our shared historic experience on these islands, and our common problems, would make true separation impossible. Indeed, it might lead to a new federal Unionism, perhaps even restoring Ireland to a Federal Great Britain. Now that would be new wine in old bottles.