HMS Vengeance, one of the Royal Navy's Vanguard-class submarines carrying the Trident ballistic missile (Picture: MOD).
Nicola Sturgeon, leader of the Scottish National Party (SNP), has included the scrapping of the Trident nuclear programme in a list of demands to Labour if it is to receive SNP support in the event of a hung parliament.
The SNP is willing to offer conditional support for a minority Labour government if no party wins an overall majority in this year's General Election.
The Labour manifesto pledges to renew Trident, though leader Jeremy Corbyn has been a lifelong opponent of nuclear weapons.
Ms Sturgeon told Sky's Sophy Ridge that she was "absolutely firm" on the issue, saying she has a "moral objection to weapons of mass destruction".
She went on to address the opportunity cost of Trident, saying the "tens of billions" invested in the programme would be better spent on a "conventional defence", alongside other public services.
In an article published by The Guardian, Ms Sturgeon wrote: "This question is increasingly put to politicians as some kind of virility test.
"The subtext is that to be a credible political leader, you must be willing to use an indiscriminate weapon of mass destruction – killing millions, or even tens of millions, of innocent people."
She added that, since the Second World War saw the United States drop atomic bombs over Hiroshima and Nagasaki, weapons development means "a modern nuclear strike would not be counted in the tens of thousands, but in the millions".
Trident incorporates the use of four Vanguard-class submarines armed with ballistic missiles, and operates at HMNB Clyde.
The SNP's Westminster leader, Ian Blackford, has reiterated the significance of the Trident dilemma for the party on BBC Radio 4's Today programme.
He said: "The effectiveness of this as a deterrent isn't the same as it was in decades gone by.
"It is an enormous waste of money, and I think it is right that we stand by the needs of our defence forces."
Mr Blackford added that continued investment in nuclear capabilities is wrong "from a military point of view, from an ethical and from a moral point of view".
Ms Sturgeon has also insisted that Labour stop Brexit and commit to a Scottish independence referendum in the New Year.