British members of Parliament will vote later today on multi-billion dollar plans to replace the UK’s ageing fleet of Trident nuclear submarines. As Richard Bestic reports from London, Britain’s independent nuclear weapons arsenal is hugely controversial opinion in Parliament and the country.

At any time of night or day, a British nuclear submarine is patrolling international waters around the world in readiness for nuclear war. A Fleet of four each armed with Trident thermonuclear weapons.  Based on the west coast of Scotland, the fleet’s mission for the last two decades, according to the UK’s Defence Department, "to deter the most extreme threats to national security."

In one of his last acts before leaving office, Britain’s former Prime Minister David Cameron committed to replacing Trident.

"The nuclear deterrent remains essential in my view, not just to Britain security but as our allies have acknowledged  here today, to the overall security of the NATO alliance," said David Cameron, former UK PM.

A view not universally shared in Britain. Opponents say nuclear weapons are a Cold War hangover unsuited to modern conflict and Trident’s estimated $55 billion dollar replacement is too costly.

"Well, it’s an enormous amount of money on a weapon of mass destruction that if used would kill millions. The idea that we could ever use this is just appalling; immoral; illegal. We oppose it because it doesn’t address anything we need to be dealing with today," said Ian Chamberlain, Campaign for Nuclear Disarmament.

In Parliament, Scottish MP’s say costs on Trident’s replacement are running out of control, while the official Labour opposition is divided, with many Members of Parliament defying their leader.

When it comes to the vote, an overwhelming number of Members of Parliament can be expected to vote in favour of renewing Britain’s independent nuclear weapons. However, in the country the mood may be changing. A survey by the Scottish Herald suggests less than half the population now support the country having nuclear weapons.