If the UK Government wants to sell Trident renewal to Scots voters, I'm not sure George Osborne makes the ideal salesman. The Chancellor's intervention in the referendum campaign was a near disaster. Almost from the moment he issued his diktat on the pound, support for the Union began to wilt.

Yet, there he was again yesterday unveiling a £500 million investment in Faslane, which he said would be put at risk by “the unholy alliance of Labour’s left-wing insurgents and Scottish Nationalists”.

He should have a care. This unholy alliance accounts for all but one of Scotland's 59 MPs.

Labour's sole Scottish MP, Ian Murray, told voters in Edinburgh South before the election that he, like the SNP, opposes renewal. The Liberal Democrat MP, Alistair Carmichael, opposes like-for-like replacement.

And the unholy alliance is growing day by day. The new leader of the Scottish Labour Party, Kezia Dugdale, has announced that her party conference is to have a free vote on Trident. This may not be unconnected to the fact that unilateralist Jeremy Corbyn could be about to become leader of the UK Labour Party.

Even the UK Liberal Democrat leader, Tim Farron, is increasingly sceptical about Trident, which possibly explains why Mr Osborne has jumped the gun this week: he wants to make Trident a done deal before the decision on renewal is taken by Parliament next year.

Trident is arguably at greater risk today than at any time since its submarines became operational 20 years ago. The SNP has won the greatest landslide in electoral history on an unequivocal commitment to remove nuclear weapons from the Clyde.

So long as both the UK’s main political parties were behind Trident renewal it was just about possible to ignore this. But with the likelihood of a new Labour leader also calling for Trident to be scrapped, this is beginning to look untenable.

It is assumed that Labour would split if Mr Corbyn wins and that the pro-nuclear MPs would all join the Tories or set up on their own. But I'm not so sure about this. Tony Blair might, but he isn't an MP.

Okay, Andy Burnham may resign from the front bench. But we might discover that the Parliamentary Labour Party isn't actually very enthusiastic about defending indefensible weapons of mass destruction.

The Government's majority in the Commons is only 12 seats and there are a number of Conservatives such as Crispin Blunt who oppose Trident renewal and have voted against it in the past. He did so on the not unreasonable grounds that £100 billion could be better spent on the ill-equipped British army.

Even the defence chiefs have noticed that Trident is on a shoogly peg, which is why there’s been a sotto voce debate in military circles about possible alternative sites for the system. Devonport near Plymouth is the most obvious. But it's generally agreed that nuclear weapons could not be located there because of – wait for it – safety considerations.

Now, at this point we'd normally expect a gaggle of Scottish Labour politicians led by Jackie Baillie MSP to be leaping up to echo the Chancellor's claims about job losses at Faslane, as she did during the referendum campaign. She even endorsed the suggestion by the-then Tory defence Secretary, Philip Hammond, that 11,000 jobs would go.

Yesterday, the silence from Scottish Labour's Trident enthusiasts was deafening. They may not have joined the unholy alliance, but they realise that the Times They Are A-changin'. They're no longer so keen to leap onto platforms with Tory ministers to defend nuclear weapons. In fact, it seems hard to believe that they ever did.

No one seriously believes that 11,000, 7,000 or even 2,000 jobs would go if Trident were decommissioned. HM Naval Base Clyde could still house conventionally-armed submarines, like the Astute class which is based there.

Indeed, there's no reason why the Trident carrying Vanguard submarines could not continue to operate without carrying warheads designed to destroy Russian cities. At present they go on patrol without their weapons being targeted, for the obvious reason that there is no conceivable target for Trident missiles. It is a dangerous anachronism.

Serious concerns about security on the weapons system were raised earlier this year by the whistle-blower, William McNeilly, who worked on it. But a greater risk is probably sending convoys down the A82 and M6 every year taking the warheads for servicing to the Atomic Weapons Establishment at Aldermaston in Berkshire.

There have been numerous incidents. If, one day, they were to take a one-way trip and stay in England, would anyone notice?