David Cameron declares war on Scotland

The independence referendum may have been lost, but the SNP continues to slowly advance towards its ultimate goal. David Cameron's partisan selfishness is slowly driving Britain apart.

That the SNP's spectacular goading is behind the Conservatives' openly self-centred manoeuvring should not be in doubt. When yesterday's draft bill on Scottish devolution was published, first minister Nicola Sturgeon made clear her party was prepared to break its longstanding principle that it steers clear of any English-only matters. It was a brilliant move that has flushed the Tories' plottings into the open.

"If there was a vote in the House of Commons to repeal the privatisation of the health service that has been seen in England, we would vote for that because that would help to protect Scotland's budget," she told the BBC. This shift matters because, while the SNP only have six MPs right now, they are very likely to have at least 20 more after 2015.

Both Labour and the Conservatives have reason to be worried. At the weekend a Panelbase poll for the Sunday Times put the SNP on 41%, down four points, with Labour up three points to 31%. That represented a narrowing of the gap for Ed Miliband's Scottish MPs, who are moping and moaning around Westminster that they are all doomed. Even those with majorities of over 14,000 find themselves deeply pessimistic about their prospects. And the latest poll won't have helped: an Ipsos Mori poll for STV, the latest to come out, puts Labour behind by 28 points, suggesting the SNP could take 55 of Scotland's 59 seats.

Turning this promise into reality requires Sturgeon to nullify the main warning now being hurled at wavering voters: that if they back the SNP in May they'll end up with a Tory government. Hence her promise to intervene in English-only affairs to protect the kinds of things, like the NHS, that Labour MPs would be voting on anyway. It was politically necessary, but also very deftly done because it represents a new threat to the PM's ability to continue in Downing Street after May 7th. No wonder he responded so robustly – and in doing so flushed the Tories' own machinations into the open.

Sturgeon's plan, Cameron has declared, would be "wrong".

"It's only fair as a Westminster member of parliament I don't have the ability to vote on Scottish health or education or housing," he said.

"I don't see why in future SNP members or indeed Labour, Liberal or Conservatives members or Alex Salmond himself should be able to come to Westminster and have the decisive say on English or Welsh education, health service or other issues."

Complaining of 'unfairness' in this context is meaningless because every possible arrangement will be unfair to someone. Britain is an asymmetric place which already has unbalanced power arrangements: in London, in Wales, in Scotland, in England, in built-up areas now agreeing city deals, the breadth and depth of devolution are all different, but their MPs have the same say in Westminster. When Cameron talks of what is 'fair', he means 'fair' for the Conservative party's interests only.

This would not matter much if he hadn't then taken a step further than he ought to have done – by bringing the SNP's voting rights on English matters into play.

"It wouldn't be appropriate for English constituents to have a rate of tax essentially imposed on them by Scottish members of parliament," he added.

Where on earth had this come from?

Only three days have passed since George Osborne told MPs Scottish MPs would still be permitted to vote on the Budget.

And under the Conservatives' three proposals published in the government's command paper on options for English votes for English laws, there is nothing at all which suggests the SNP would be restricted from having a say on these issues.

The approach being pursued by William Hague is one of ensuring a double-veto. English MPs would be given the opportunity of voting down anything they don't like being imposed by a Labour government propped up, say, by MPs in Scotland. But the bill would ultimately have to be passed by a majority of British MPs for it to become law. That would apply to Budgets as well as everything else.

It's almost as if the Tory strategizing has been solely focused on ensuring a Conservative opposition can block Labour bills, and not at all on the possibility of a Conservative government's proposals being scuppered by Scottish opposition.

Cameron's intervention has come from nowhere. That makes it brazenly partisan. There is no regard here for what is best for the long-term stability of the UK. Instead we have a naked, grim struggle for power in which principles are harnessed for political ends, rather than being pursued in their own right.

The Conservatives have been goaded by circumstance into embarking on a constitutional struggle that is not of their making. It is the SNP that takes the credit for this. It is the SNP which will be gaining in power and influence after 2015. Sturgeon and the man who will lead the SNP in parliament after May, Alex Salmond, may have lost a battle last September. But it is entirely possible they could yet win the war.