THERESA May’s Cabinet is the flat-pack cabinet. It has a few loose screws and it’s falling apart. The Tories are completely at a loss over Brexit, openly divided, briefing against one another, plotting and back-stabbing amid rumours that May’s leadership won’t survive long after the party conference season.

The Labour Party has been gifted the equivalent of a big political hammer, and just one blow, not even a particularly well-aimed blow at that, will take the whole teetering edifice down. Instead, Labour prefer to use that hammer to hit themselves in the face.

Labour’s leadership has managed to sideline calls from party membership for a referendum on Brexit. Shadow chancellor John McDonnell has conceded that there can be a referendum on Brexit, but has ruled out any second Brexit referendum which includes the option of remaining in the EU – a move which destroys the reason for having the referendum in the first place.

The millions of Remainers who had looked to Labour to provide a credible alternative to Brexit will now look elsewhere. If you oppose Brexit, there’s little point in voting Labour. They’re just as committed to the insane British nationalist project as the Tories, but you’ll now be able to get a nationalised train to the job that you’ll no longer have after the UK economy tanks.

But continuing in the tradition of the serially inept leadership of the Scottish Branch Office, it’s in its Scottish policy where the Labour Party has proven most clueless. Richard Leonard, the man who has most recently got himself trapped in the revolving door of Scottish leadership, has announced that his party will fight the next General Election with a solid manifesto commitment to reject any prospect of a second independence referendum.

Labour has rejected the Claim of Right of 1989, renewed and reaffirmed by its own MSPs in 2012, and again on July 4 this year, by MPs in Westminster. That Claim of Right states that the people of Scotland have the sovereign right to determine the form of government best suited to their needs.

However, now Labour is apparently telling us that a future Labour government of Jeremy Corbyn will have a mandate to refuse a Scottish independence referendum even if the Labour Party fails to secure a majority of votes or MPs from Scotland. Labour no longer upholds the Claim of Right. Labour now believes that it’s only Westminster which has a sovereign right to determine the form of government best suited to the needs of Scotland, and can do so on the basis of the votes of MPs from outwith Scotland.

The Claim of Right is the document which doesn’t merely underpin the devolution settlement, it also represents the political foundation of Scotland’s place within the UK. If Labour has unilaterally decided to rip that claim up, then all by itself that counts as a material change of circumstances which justifies a second independence referendum, with or without Brexit.

The destruction of the Claim of Right fundamentally alters the relationship of Scotland to the other nations of the UK, and does so without the consent of the Scottish people or their elected representatives.

Independence supporters who lent their votes to Corbyn in the last General Election won’t make that same mistake in the next one. Vote Labour, vote to have your democratic rights taken away. It’s perfectly OK for a party to oppose independence. Democracy depends on parties having that right.

What’s not OK is for a party to demand that the right to support independence is taken away from others. That’s the death of democracy. Labour is turning itself into Spain’s Partido Popular. Labour tells us that the key theme of its party conference is that socialism in 2018 means extending democracy to every part of society, except for viewers in Scotland.

The obvious question is, “What was Labour thinking?”, but the equally obvious answer is that the party wasn’t thinking at all. Labour in Scotland can’t get past its atavistic hatred of all things SNP in order to consider the implications of its own decisions.

Labour, just like the Tories, repeats the mantra that the result of the referendum of 2014 must be respected. A referendum result can be preserved in stone forever, or it can be democratic. It can’t be both. When a people have no right to change their mind in the light of changed circumstances, there is no democracy. That’s where we are now with the British nationalist parties in Scotland. They insist that Scotland has no right to change its mind even though circumstances have changed. They demand that the vote they secured in 2014, on the basis of promises that they never kept, be respected so that the electorate have no means of holding them to account. That’s not democracy.

The British nationalist parties in Scotland are getting desperate.

They can see that the writing is on the wall for their so-called Union that is no Union at all. They know that with English Votes for English Laws, with Brexit, with the farce of the Vow, that they have nothing positive to offer the electorate of Scotland in a future independence referendum. They have destroyed their own best arguments from 2014, the argument that the UK represented the status quo, that it was independence which represented insecurity and instability. They cannot argue that independence is the choice of narrow xenophobic parochial nationalists when they’re supporting Brexit.

The best bet of the British nationalist parties – their only bet – for keeping Scotland a part of the UK is to prevent another independence vote from happening at all. They know that when there is another vote on the subject, Scotland will vote to leave this dysfunctional farce of the UK. They can only prevent that happening by stopping a vote from happening.

But when you stop the people from having a say, you’re no longer a democratic party. The choice facing Scotland now is independence and democracy, or an increasingly anti-democratic future as a silenced and marginalised province of an isolationist UK.