Theresa May has been urged to delay the parliamentary debate on Trident renewal.
The new Prime Minister was called on by the SNP's Westminster leader to pause the vote until MPs know the full cost of the UK's nuclear deterrent.
In a statement reported by the BBC, Angus Robertson said the decision needed "proper scrutiny".
"Trident is an immoral, obscene and redundant weapons system - and the decision on whether to renew it is one of the most important votes this parliament will ever take," Mr Robertson said.
"Having spent the best part of a month engaged in backstabbing, score-settling and navel-gazing, neither the Tories nor Labour are in any fit state to be giving proper scrutiny to decisions as important as this."
He added: "The enormous cost of Trident appears to be spiralling out of control - before MPs can come to an informed view, they must have access to full costs across the lifetime of the programme."
His comments came as the Labour Party's deputy leader Tom Watson said that abandoning the deterrent would remove the "the protective curtain behind which freedom and democracy have flourished in countries across eastern Europe".
"To abandon our deterrent in that context would be a grotesque abandonment of our friends at a time of great peril," he said.
He added that those who vote against the renewal are in favour of putting "livelihoods of thousands of skilled British workers" at risk and inflicting "real harm" on the UK's defences.