MPs are set to vote on Monday evening whether or not to renew Britain's £40 billion Trident nuclear deterrent.
Prime Minister Theresa May will urge MPs not to gamble with the safety of British families, adding that it would be "grossly irresponsible" not to back it.
The Labour party is expected to split on the issue, with the shadow cabinet calling on MPs to sustain but deputy leader Tom Watson and leadership candidate Owen Smith set to back Trident.
However, despite the opposition of the SNP and less than half of Labour MPs, the Government is expected to win the vote and renew the submarine deterrent.
Mrs May is expected to say that the global nuclear threat has "increased" rather than gone away in recent years.
The Tories committed in their 2015 general election manifesto to replacing the Vanguard class of submarine which carries Trident missiles with four new successor class boats.
The Government says the latest estimate puts the cost of the four successor submarines at £31 billion over 20 years with a £10 billion contingency - on average 20p in every £100 the state spends.
A renewed Trident programme will be operational until the 2060s.