Shadow defence secretary Emily Thornberry gave a series of interviews this week that touched on whether a Labour government would be prepared to use nuclear weapons.
Labour’s official policy is to support the replacement of the UK’s Trident deterrent with a new nuclear missile system.
But Labour leader Jeremy Corbyn is a lifelong supporter of nuclear disarmament, has voted against renewing Trident, and in 2015 said he would not use it.
Ms Thornberry suggested that the decision to press the nuclear button might be made collectively, rather than by Mr Corbyn alone.
This raises the question of how Labour would deal with the “letters of last resort” protocol – in which a new Prime Minister personally gives written orders to nuclear submarines on whether they should retaliate in the event of a catastrophic nuclear strike on the UK.
What’s Labour’s policy?
Labour’s last manifesto stated that the party “supports the renewal of the Trident nuclear deterrent”. But Labour is divided on the issue.
In a Commons vote in 2016, 140 Labour MPs supported government plans for Trident renewal, while Jeremy Corbyn, shadow defence secretary Nia Griffiths and 45 other Labour MPs voted against it. Ms Thornberry did not vote.
In 2017 the shadow foreign secretary gave an interview with LBC saying she was “sceptical” about Trident. She declined to confirm that it would remain Labour policy after a defence review.
Mr Corbyn and Ms Griffiths responded by publicly restating Labour’s commitment to replacing Trident.
Asked about the party’s policy in an interview with Good Morning Britain on Tuesday, Ms Thornberry said: “Our position is that the decision has been made and so we’ve moved on.”
Ms Thornberry told GMB: “No leader has said one way or the other until very recently whether they were prepared to use the nuclear weapon or not.
“So, we’ve had Conservative leaders recently saying they would press the button. We’ve had Labour people recently saying they wouldn’t press the button. I’m of the view that it’s best for us not to say one way or the other whether we would use it or not, just as we have done for generations.”
It’s true that British Prime Ministers have generally pursued a policy of “deliberate ambiguity” – not saying whether, or in what circumstances, they would authorise the use of nuclear weapons. This convention has been broken several times in recent years.
In a BBC interview in September 2015, shortly after he became Labour leader, Mr Corbyn was asked: “You wouldn’t use them?” and he replied: “No.”
We’re not aware of any other potential leader ruling out the use of the nuclear deterrent, although Conservative Prime Ministers have removed some of the ambiguity by stating that they would use Trident.
Shortly after Mr Corbyn’s interview, the then-Prime Minister David Cameron said: “There are circumstances in which its use would be justified.”
In July 2016 Theresa May was asked in her first Commons speech as PM if she was “personally prepared to authorise a nuclear strike that can kill a hundred thousand innocent men, women and children?” She replied: “Yes.”
On Tuesday, Ms Thornberry went on to suggest that it might not be Mr Corbyn alone who made the final call, saying: “I don’t necessarily believe that will be a decision made by one individual. I suspect that the way that Jeremy makes decisions is that he takes advice and we work collectively.”
She also said it was “impossible” to say in advance what the decision would be:
“The use of a nuclear weapon is a decision on a level that no politician anywhere has to make – it is completely on its own. And no one in the end knows how they would use it, whether they would use it.
“If we are in circumstances where we are under threat, it’s impossible, I think, for any human to say whether they would be prepared to kill millions.”
Letters of last resort
In fact, British Prime Ministers are asked to decide – alone and in advance – what they would ask their submarine commanders to do if the government was knocked out by a nuclear attack.
It has been widely reported by multiple sources that one of the first jobs of a new PM is to write the sealed orders that are kept in the safes of the four nuclear-armed submarines which roam the seas continuously as a deterrent to Britain’s enemies.
If the submarine commanders lose all contact with home, it is thought the letters can empower them to retaliate with nuclear missiles – although the precise text has never been revealed.
So if Mr Corbyn was elected Prime Minister, he personally would have to make a decision on Britain’s nuclear weapons strategy almost immediately.
We asked Labour whether Mr Corbyn would comply with the “letter of last resort” protocol, and whether the letter would be decided collectively or by him alone.
We also asked them whether it’s still Mr Corbyn’s position that he would never authorise the use of nuclear weapons.
And we asked whether how the joint decision-making process Ms Thornberry mentioned would work in a nuclear crisis. Would cabinet members be able to persuade, overrule or outvote the Prime Minister?
A spokesman simply told us: “Jeremy Corbyn will do whatever is necessary to keep our country safe.”
Our understanding is that Mr Corbyn would listen to advice from others but the final decision on whether to authorise the use of nuclear weapons would be taken by him.