Prime Minister Theresa May has been urged by the SNP to delay Monday's vote on Trident renewal to allow "proper scrutiny".
The party's Westminster leader Angus Robertson said it was "one of the most important decisions parliament will ever take."
He said MPs must know the renewal costs before they can have an informed view.
Former prime minister David Cameron said Trident was an "essential deterrent" for Britain's security.
The SNP will vote to reject the renewal of Trident.
While the majority of Labour MPs are expected to vote in favour of Trident renewal, Scottish Labour party delegates overwhelmingly backed a vote to scrap the UK's Trident nuclear missile system at their conference last year.
Mr Robertson said: "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.
"Over the last few weeks we have witnessed unprecedented political turmoil, as the entire Westminster system was shown to be completely unprepared for the prospect of a Brexit vote.
"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: "It would be both morally and economically indefensible for the UK government to commit to spending hundreds of billions of pounds on weapons of mass destruction - even more so at a time when they are cutting funding for public services.
"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."
Thousands of people attended 36 protests against Trident renewal at towns and cities across Scotland on Saturday.
It is understood the UK government has no plans to move the missile system from Faslane on the Clyde.
A source close to Defence Secretary Michael Fallon said: "This government was elected on a manifesto to build four ballistic missile submarines to replace the current fleet. We committed to hold a vote and we need to have this now given the time it takes to build and test the submarines.
"All MPs will have to decide whether to gamble with our national security. The SNP will be voting to weaken our security and to close Faslane, Scotland's biggest employment site."