FALKIRK has long been a kind of petri dish for Scottish politics, an experimental place where strains grow and develop in a local culture, becoming objects of study and fascination for the rest of us.

We had the Dennis Canavan era when a patently decent and able politician felt sufficiently strongly about being denied the right to stand for the Scottish Parliament for the party he had been born into, that he stood against it as an independent and won. He then quit his Westminster seat to concentrate on Holyrood and forced a by-election. The Goldie brothers ran the local Labour machine, so the New Labour hierarchy, in its pomp in 2000, backed as favoured candidate a former Army Major, Eric Joyce. That went well, didn't it?

Now we have the pugilistic Mr Joyce standing down after a string of disgraceful episodes and the almost equally-unseemly squabbling for the Labour nomination begins again. Only this time the fall-out reaches all the way to the office of Leader of the Opposition at Westminster.

This is because the latest fight isn't just about a local selection battle, but a UK battle for the moral and political leadership of the Labour Party and what used to be called the Labour Movement.

The Unite union is attempting to spearhead a campaign against Labour's acceptance of the Tory austerity agenda, and, it now appears, against the very leadership of Ed Miliband, the candidate it backed for the leadership but who it now sees as having betrayed the unions' faith since his election.

It's all a bit like Google maps. You start with the Leader of the Opposition at Westminster, you zoom down to the unions which backed his candidacy, down further you get one particular union with a strategy to recruit activists around the UK, and below that you get to the Falkirk selection controversy as the most obvious local example of what Unite has been up to. The street view, if you will.

And these, of late, have been mean streets. Anyone immersed in the history of the Labour movement and the way the link was cynically severed during the New Labour era may have some sympathy for unions seeking to re-assert a degree of influence in the age of austerity. But a good cause can be given a bad name.

Lest anyone feel sympathy for Unite and the blatant attempt to hi-jack the Falkirk nomination can we point out the original memo on which our sister paper the Sunday Herald led the charge on this story. "Unite, following regional and local consultation, is very likely to back Unite member and activist, Karie Murphy.

"Using similar methods to Garston and Paisley but at a much more intense level, led by the potential candidate, and very much supported by the local activist basis, especially at Ineos, we have recruited well over 100 Unite members to the party in a constituency with less than 200 members; 57 came from responses to a text message alone."

That Unite was having a recruitment campaign at Grangemouth oil refinery was a good thing. That it was nakedly doing it to punt its preferred candidate in a by-election was not. It will now be of interest to see whether Ms Murphy – who has been a bit hokey-cokey about whether she is still standing – will proceed. If she does not, it will amount to an admission that she could not win without a rigged contest.

The Labour Party announcement about "special measures" does not mean an imposed candidate in Falkirk, but it does mean that the clock is re-set on all those new members signed up and ultimately the selection will be a head office job.

Local constituency party activists have told The Herald that they are delighted that they have got their party back, that Unite arrived, hi-jacked the structure and ceased having full CLP meetings, relying instead on "business meetings" of a smaller group. Politburo meetings sounds about right.

The source added: "It was classic entryism. They were in power without having to have control over the whole membership. There is a real sense of relief among members that there seems to be some sort of solution."

The real problem is that entryism happens when political party memberships fall below a critical mass of numbers. That the party of Keir Hardie or Willie Ross or even Donald Dewar has only 200 members in Falkirk says it all. To jump away from street view, might Mr Miliband want to reflect on why the Falkirk Labour Party has come to this?

Part of this must be the succession of losses to the SNP at Holyrood and to the Tories and their Liberal Democrat allies at Westminster. But part of that must also come from the debilitating effect of an ideological pocket skilfully and regularly picked by your closest opponents on the ground. Labour and the SNP plough exactly the same furrough in terms of potential support. The SNP shed relatively few votes last week in Aberdeen Donside, while Labour made some progress with a candidate who was a Porsche-driving property developer.

Of course the unions have a right to involvement in and engagement with the Labour Party. The trouble is this two-way respect broke down around the time of beer and sandwiches with Harold Wilson. But the truth is that when the IMF told Britain its cuts were wrong-headed because they blunted growth, and a Labour Shadow Chancellor chose to mimic Tory austerity cuts instead, trade unions were entitled to dissent.

The unions and the poverty experts can rightly argue that so-called austerity is less a rescue plan and more an ideological cul-de-sac, that even the most modest of growth could help get us all out of this mess, even that trade unions do great work arguing on behalf of pensioners, not just those currently paying dues.

The unions are even entitled to point all of this out to Mr Miliband and Ed Balls, possibly even over beer and sandwiches, which were never a bad thing. David Cameron had big donors in for dinner at Number 10 regularly, which could be called "dirty money" or "cash for access."

But trade unionists represent millions of people in the UK. It is absolutely right that TUC leaders should have access to Downing Street, but compared to the dialogue at Bute House there is little sign of mutual respect there.

The Tories aren't speaking to the unions. Mr Miliband's election to the Labour leadership was swung by the unions, but he is now in denial mode, encouraged by a hugely hostile London media. In Scotland Alex Salmond cosies up to the unions all the time and at the STUC they practically stick a garland round his neck.

There is an irony, surely, that Ed Miliband, the "Red Ed" who only beat his New Labour brother David to the Labour leadership on the back of trade union votes, is now at war with some unions. But some of these former allies are being blatantly manipulative and do the movement no favours. Unions have a duty to make their case, but do not a right to hijack democracy.

Iain Macwhirter is away.