IT must have been a poor imitator of Jeremy Corbyn who took over on Monday night, after the real McCoy finished his speech at the STUC conference in Aviemore. Surely the man himself wouldn’t have stormed down to Dunfermline, blamed the Scottish Government for the evils of his Westminster opponents and expected the Scots to swallow it?

At lunchtime, surrounded by his fellow trade unionists, Mr Corbyn implored us to reject the “vicious” Tories, stand up for working people and end the need for foodbanks. He urged us to focus on ending poverty rather than breaking up unions. He vowed to protect pensions and take on the tax avoiders. It was all going so well.

This was surely the kind of politics Labour members had hoped for when they backed the veteran MP as leader: an inspiring call for citizen solidarity and a challenge to the ruling elite. No spin, no smears, no dirty tricks – just a positive message of change, falteringly delivered by a kindly chap who hadn’t rehearsed properly. And who bizarrely seems to believe that four extra bank holidays will be enough to sweeten the deal for anyone who isn’t quite buying his up-the-workers vision.

Then there was Dunfermline. At this point the Jeremy Corbyn who promised a “kinder, gentler politics” presumably gave his understudy the baton and went for a lie down. How else to explain his incoherent rant against the SNP Government?

Scottish voters are fatigued, but they aren’t daft. They know that when Mr Corbyn’s evil twin says the Scottish Government has “overseen” an increase in child poverty, the truth is that Holyrood has no power to halt so-called welfare reform or set the UK minimum wage. That when he says “many Scots rightly expect the Scottish Parliament to protect them from the vicious Tories” he’s insulting the intelligence of an electorate that understands better than ever the distinction between reserved and devolved matters. He’s hoping Scottish voters will a) believe the SNP could and should have ended child poverty by now, and b) deny the party General Election votes as a consequence.

Unwittingly, he may actually have done the SNP a favour by proclaiming it a “poor imitation” of a left-wing party. After all, plenty of SNP supporters are not particularly left-wing, with centre-Yes voters buying into a party ideology that is blandly, unthreateningly “progressive” because they see it as the best route to independence. If the SNP is closer economically to the New Labour of Blair than the New Old Labour of Mr Corbyn, that’s clearly no obstacle to electoral success. Tony Blair won three General Elections, after all; Mr Corbyn has barely managed to cling on long enough to contest one.

Of course, the Labour leader must be peeved that he didn’t get a shot at Scotland before the SNP fitted all his party’s safe seats with ejector springs. And Mr Corbyn’s greatest weakness as a leader is that he isn’t very good at hiding when he’s peeved. Witness the way he lost the heid at BBC political correspondent Paul Brand earlier this month, when asked if he was considering stepping down. He then compounded matters by tweeting footage of the embarrassing encounter, in which he furiously pointed fingers and blamed dismal poll results on poor media coverage of his policies. Witness his declaration in Dunfermline that the SNP has “failed abysmally” to tackle inequality and “failed in government in all policy areas”. Failure in all policy areas? Gosh, how on earth have the Scots failed to notice this, and failed to switch their votes accordingly? It’s starting to sound like Mr Corbyn wants to scrap the Scottish Parliament altogether.

He may also have boosted the SNP’s General Election prospects by failing to focus on what should have been his key message: that only Labour can unseat the hard-right Tories currently in power. By claiming the SNP has not fought against poverty and inequality he only serves to draw attention to the fact that it absolutely has, noisily and prominently, albeit to little effect. News of his hyperbolic attack came on the day when Holyrood fiercely condemned the family cap – a UK Government policy over which it has no control, despite what Ruth Davidson might suggest. This timing only serves to demonstrate UK Labour’s ignorance of Scottish political affairs.

It’s one thing to assert that Labour will not enter into an alliance with the SNP – ruling out coalitions is all the rage these days – but there’s been nothing to stop the two parties working together on an issue-by-issue basis since the 56 nationalist MPs took their seats on the green benches. One might have expected left-wingers to seize on the “nasty party” policy of restricting tax credits to a family’s first two children – a policy announced in George Osborne’s 2015 Budget. Instead they have seemed happy for a poor imitator, the SNP’s Alison Thewliss, to do the heavy lifting here. In line with her party’s centre-reasonable approach, Ms Thewliss cannily focused on the headline-grabbing “rape clause” rather than the restriction of benefits itself. The latter, considered on its own, was likely supported by many middle-income Scots who call themselves progressive but baulk at the idea of big families living off the state. But Tory defence of the policy has been completely drowned out thanks to a well-organised campaign led by a confident, well-organised SNP.

The family cap presented a perfect opportunity for Mr Corbyn to challenge the “scrounger” rhetoric of the Tories head-on, and to shame the Government for a policy that was inhumane, illogical and unworkable. And where was he? Presumably busy fighting with his own party about their disagreement du jour. If this week’s speech in Dunfermline sounded like it was scribbled on the back of a copy of Socialist Worker, that’s probably because Mr Corbyn was fielding frantic calls about his refusal to back Trident renewal, or his wishy-washy Brexit stance, or his inability to keep cool under questioning about his leadership abilities.

While some voters in Scotland are happy to dance on the grave of a Labour Party they feel has deserted them, many others will be watching Mr Corbyn’s car-crash campaign from between their fingers. With his attempt to blame the SNP for the mess the UK has got itself into, he has shown himself to be a poor imitation of an opposition leader.