A war of words has broken out over Trident renewal with Scottish Nationalist leaders accusing the UK Government of arrogance while Chancellor George Osborne railed against Labour and SNP unilateralists, saying they were putting Britain's security at risk.

Angus Robertson, the Nationalist leader at Westminster, is thought to be mulling over whether or not to use an SNP debate in the Commons next Wednesday to draw the battle lines over Trident and put a destabilised Labour Party on the spot.

In January at Westminster, a Nationalist motion against Trident renewal was heavily defeated by 364 votes to 37; among those supporting the motion were just 19 Labour MPs, including leadership frontrunner Jeremy Corbyn and six now ex-Scottish Labour Members.

But now with an enlarged SNP group and a Labour Party disunited by the leadership contest – Shadow Scottish Secretary Ian Murray, Labour’s only Scottish MP, has made clear he is against Trident renewal – Mr Robertson might well think this an opportune moment to test the political water ahead of the main-gate decision, due early next year, on creating a new generation of nuclear submarines, and to emphasise what the party believes is a "democratic deficit" between Scotland's distaste for nuclear weapons and the Tory Government's devotion to them.

The totemic issue is also likely to be debated intensely at this autumn’s Scottish Labour Party conference, at which Mr Corbyn, win or lose, hopes to speak, and when new leader Kezia Dugdale, who is in favour of Trident renewal, could find herself out of step with most of her own colleagues and party members.

As Mr Osborne visited the naval base on the shores of Gare Loch in Argyll and Bute to announce a further £500 million upgrade to expand its infrastructure, including jetties and seawalls, he declared that the investment was a "massive boost" for Scotland and the defence industry, securing almost 7000 defence jobs.

The money – more than £1 billion has already been spent in preparation for Trident renewal – will be used to “ready” Faslane as it is due to become the home to all of the UK’s nuclear and conventional submarines from 2020.

But he was strongly challenged by the SNP. Nicola Sturgeon said: "I want to see Faslane have a strong future as a conventional naval base but this is an arrogant decision by the Chancellor to try to pre-empt Parliament's decision on the replacement of Trident.” The UK Government is expected to make its main-gate decision on Trident renewal early in 2016.

The FM added: "If the Chancellor's got £500m to spend, then he'd be better advised to spend it on health, education, giving young people the best start in life and reversing some of his cruel attacks on the most vulnerable."

Earlier, John Swinney, her deputy, noted that if savings were made by not renewing Trident, then it would enable money to be invested in conventional forces and "as a consequence enable us to properly protect our country".

He accused Mr Osborne of “making the wrong moral choice" to prioritise investment in weapons of mass destruction over the protection of the most vulnerable in society.

And the DFM claimed the Tory frontbencher had timed the announcement “partly to stir it up within the Labour Party; to exacerbate some of the issues around the stance taken by Jeremy Corbyn”.

A similar point was made by Willie Rennie, the Scottish Liberal Democrat leader, who suggested the Chancellor was being provocative, saying: “He's come up here in a big flash to try and provoke the anti-Trident sentiment amongst quite a large population in Scotland.

"We've not even had the debate on Trident. I would rather have seen that debate coming in a very reasonable and sensible way."

But Mr Osborne hit back, asking “in a very uncertain world” were people content to throw away Britain's ultimate insurance policy.

"Can Nicola Sturgeon or Alex Salmond tell me what the world is going to look like in 2060, because that is when we are making this decision for?" He added: "I don't think they can.”