JOHN McDonnell is one of the more admirable Labour politicians around today. An elected politician for close on 40 years, he stayed true to his beliefs through the Blair years when a whole generation of Labour left wingers traded their principles for glittering ministerial careers. McDonnell also gives the impression of being the astute political brain behind Corbyn’s New Old Labour Party.

But like his friend and leader, McDonnell has a blind spot when it comes to Scotland. The two men have been entrenched in London Labour politics for 40 years, which may at least partly explain that astonishing lack of insight.

A few months back, McDonnell wrote an article in the Daily Record whose central point was to brand the SNP the “party of austerity”.

He should perhaps have paused to ask himself how it could be possible that areas like Glasgow, Lanarkshire, Dunbartonshire, Ayrshire and Dundee – some of the strongest bastions of working-class resistance anywhere in the UK to the Thatcher government – are still supporting a “party of austerity” 11 years into its leadership.

Last week, McDonnell got himself even more tangled up when he supported Tory tax cuts to the better off. That begs another question for the shadow chancellor. Does he believe that the Scottish Government should fall into line with Westminster and cut taxes for the upper middle classes? And if not, why not? Why would the deputy leader of a self-styled Unionist party argue that the affluent parts of England and Wales should pay lower taxes than their Scottish counterparts?

Alternatively, if John McDonnell believes that the Tory tax handout should be replicated in Scotland, where does the Scottish Government find the £400 million shortfall in its budget? By cutting public expenditure? By increasing austerity?

I don’t always see eye-to-eye with the Scottish Government and I’m never afraid to voice my criticisms. We won’t build a vibrant new nation-state by playing a game of follow my leader. The independence movement should be a place where different ideas and perspectives can flourish side by side and be respectfully debated.

But praise too where it’s due – in this instance to the First Minister and her Finance Minister Derek Mackay, for ruling out lavish tax breaks for the better off in Scotland. And I hope that on this issue they resist any pressure to compromise. Already we have howling packs of Tories and right-wing media commentators baying for more money to be showered on those who need it least.

Come December – Scottish Budget Day – we can expect heavy congestion on the southbound A74 as headteachers and senior managers flee across the border, economic refugees ground into poverty by a tyrannical Government in Holyrood. After all, that’s what happens every day in Denmark doesn’t it, where the higher tax rate is 55% compared to neighbouring Germany’s 47%.

In the real world, Danish emigration is about 20% lower per head of population than emigration from the UK, where the wealthier residents enjoy one of the most lenient tax regimes. And I despair for anyone who really believes that thousands of well-paid professionals will be leaving their jobs, selling their homes and uprooting their families to move hundreds of miles away – all for the sake of bumping up their take home pay by less than 20 quid a week.

Handing out tax breaks to high earners is not just bad politics, its bad economics too. You hand over another grand to someone who already earns £60,000 a year, chances are it will lie in a bank account or a shares portfolio. Or maybe it’ll be spent on an extra holiday abroad with no benefit to Scotland.

Give that money instead to someone at the lower end of the scale and they’re more likely to spend it locally, creating what economists call a multiplier effect that introduces new jobs and secures livelihoods. Or, plough that money into public services and you create jobs and generate economic activity many times greater in magnitude than the initial investment.

I’m not going to be so crude as to accuse John McDonnell of buying into neo-liberalism because he’s endorsed tax breaks to the well-off. And I’m highly sceptical about the motives of his Blairite opponents within the Labour Party, including in Scotland, who have seized a rare opportunity to attack their leadership from the left. These are the same people who cheered on Gordon Brown when he slashed corporation tax from 33% to 28%. Their driving motive is not fairness and equality but to undermine Corbyn and McDonnell to help pave the way for the rebirth of New Labour.

McDonnell’s motive on the other hand is tactical. He believes that if he opposes these income tax cuts, he will sabotage Labour’s ambition to win power in the House of Commons. And therein lies a further conundrum for Labour Unionists. They claim that there is no political divergence north and south of the Border. That Scotland’s supposed left-of-centre culture is a myth. That we should all march together towards social justice.

But the very fact that in an age of food banks, rising child poverty and ruthless cuts to public services, a Tory Chancellor can propose tax cuts to the well off, and win the support of a dyed-in-the wool socialist shadow chancellor, exposes the continuing strength of Thatcherite values across whole swathes of southern England.

And the fact that the Scottish Government, with the support of Scottish Labour, will refuse to follow suit underlines the fact that Scotland is different. Unionists can argue differently until they are red, white and blue in the face – but that tale of two parliaments demonstrates yet again that an independent Scotland has the potential to lead the other nations and regions that currently make up the UK towards a future where the values of Thatcher, Blair, Cameron and May start to fade into the mists of history.