All changed, changed utterly... Yeats's oft-quoted line springs all too readily to mind when contemplating the Scottish Labour Party's position on an independence referendum.

Only nine days ago it was simple. Along with the Liberal Democrats and the Conservatives in Scotland, Labour would vote against any referendum bill brought by Alex Salmond and his Nationalists.

For Unionists there was nothing to apologise for in backing this policy. The Nationalists' cry that most Scots supported a referendum was based on a wilful deception. What polls had shown was that if independence was ever to be decided upon, then it was best to decide it by referendum. Polls have never shown that people were demanding a referendum because they wanted independence. The Nationalists persisted with the myth that all Scotland was desperate for a referendum and now, apparently, Wendy Alexander has bought into that myth. Not only that, she made it clear on Sunday that if the SNP bring their bill to the Scottish Parliament in 2010, the worst Labour will do is abstain.

So, even if Labour does not like the referendum question as it will be stated in the SNP bill, even though they may have doubts about how the referendum is to be conducted, Labour will not oppose it. In other words, Ms Alexander has closed off any escape route her party might have had.

This is hugely important because it means that a referendum in 2010 is now inevitable. And for Ms Alexander to call on the Lib Dems and the Conservatives to support this new position shows the arrogance and self regard of the woman. They at least have been consistent. They, at least, have put the Union above narrow political tactical advantage (which, in any case, has now disappeared for Labour).

The Liberal Democrats, remember, could be in a power-sharing coalition in Scotland now if they had not put political principle ahead of short-term expediency - a position that appears foreign to the leader of Scottish Labour.

Mr Salmond and the SNP can now relax. Their timetable for a referendum, with the poll held in autumn 2010, is still on track. They have the votes because they have Labour's tacit support. The word “incredible” does not do this political nonsense justice.

Whether or not Mr Salmond wins the referendum is a moot point. But Unionists should beware. With a likely Conservative Government at Westminster, and a Labour Party emasculated by Ms Alexander's wilful inconsistency, the omens will be good for Mr Salmond.If he loses he will find some way of abandoning his promise that independence referendums are held “once in a generation”. He will go on asking the question during a second term in power at Holyrood until he gets the right answer.

This, then, is where Ms Alexander has placed the Union. In as parlous a position as it has been in 301 years. For that, and that alone, she should resign.