MPs back renewal of UK's Trident submarines
MPs have overwhelmingly backed the building of a new generation of nuclear submarines.
After nearly six hours of at-times heated debate, they voted by 472 to 117 to approve the multi-billion pound project.
It gives formal parliamentary approval to the ongoing work to build four Vanguard-class subs to carry the UK's Trident nuclear missiles.
Making her first appearance at the Despatch Box as Prime Minister, Theresa May told MPs the threat facing Britain from the likes of Russia and North Korea - who each have the bomb - has "increased" in recent years, so renewal was a necessity.
She added: "Once nuclear weapons have been given up, it is almost impossible to get them back. And the process of creating a new deterrent takes many decades. You could not redevelop a deterrent fast enough to respond to a new and unforeseen nuclear threat.
"It is impossible to say for certain that no such extreme threats will emerge in the next 30 or 40 years to threaten our security and way of life. It would be an act of gross irresponsibility to lose the ability to meet such threats by discarding the ultimate insurance against those risks in the future."
Mrs May also said that she was willing to press the nuclear button, even if it meant the deaths of hundreds of thousands of innocent people.
However, Labour leader Jeremy Corbyn - who gave his MPs a free vote on the issue - re-iterated his position that he would never authorise the use of Britain's nuclear weapons.
He said: "I would not take a decision that would kill millions of innocent people. I don't believe the threat of mass murder is a legitimate way of going about international relations."
Mr Corbyn also angered many of his own MPs by saying he would vote against his own party's official policy, which is in favour of maintaining the UK's nuclear weapons.
In an outspoken attack, Copeland MP Jamie Reed accused Mr Corbyn of being determined to lead the party to defeat at the next election.
He said: "We're forced to accept that the refusal to accept the established policy of the Labour party and to acknowledge the achievements of the greatest Labour government is not just a knowing embrace of electoral defeat, but a very real, a very studied and a very determined desire to split this Labour party."
John Woodcock, whose Barrow constituency depends on the Trident programme for thousands of jobs, said: "What Labour's current front bench are doing is not principled. It shows contempt for the public, for party members and often in what they say for the truth."
And former shadow Armed Forces minister Toby Perkins said: "Both my parents were members of CND and I will certainly have made some of the arguments as a 13-year-old as we heard from the front bench some moments ago."
The SNP and Lib Dems said they would vote against the scheme.
Defence Secretary Michael Fallon said the cost of the project was £31 billion over 35 years of their life as he called on MPs to support it.
He said: "I would urge members on all sides of the house to do what successive governments have done, to do the right thing, not just for today but for tomorrow and vote to maintain our nuclear deterrent for as long as security conditions require it."