Theresa May has claimed Labour cannot be trusted with the defence of the country, after a row broke out within the shadow cabinet over the future of the Trident nuclear deterrent.

Jeremy Corbyn was forced to restate Labour's commitment to Trident renewal, after his shadow foreign secretary suggested the party could withdraw its support after a post-election review of Britain's defence needs.

Emily Thornberry was slapped down by pro-Trident shadow defence secretary Nia Griffith, and Mr Corbyn himself said Labour was "committed" to maintaining the deterrent.

Speaking during a campaign visit to Birmingham, the Labour leader said: "The manifesto makes it very clear that the Labour Party has come to a decision and is committed to Trident.

"We're also going to look at the real security needs of this country on other areas such as cyber security, which I think the attack on our NHS last week proved there needs to be some serious re-examination of our defences against those kind of attacks."

A party source source said: "Trident will be renewed come what may, continuous at-sea deterrent."

The nuclear deterrent would be included in a Labour government's strategic defence review, but it would be looking at issues like "costings" and how to protect it from cyber attacks, said the source.

Mrs May seized on the confusion created by Ms Thornberry's remarks to accuse Labour of being equivocal on defence.

"We have seen yet again from Jeremy Corbyn's Labour Party today that a Labour government led by Jeremy Corbyn would not be unequivocally committed to the Trident nuclear deterrent," said the Prime Minister during an election visit in west London.

"They would not be able to defend this country.

"A Jeremy Corbyn-led Labour government could not be trusted with the defence of our country."

Speaking to LBC radio on Friday, Ms Thornberry, who described herself as "sceptical" about Trident, said she could not guarantee what the outcome of the review would be.

Asked if she could confirm the missile system would remain as Labour policy, Ms Thornberry said: "Well no, of course not, if you are going to have a review, you have to have a review.

"Overwhelmingly, we need to make sure that our policy is up to date and meets 21st century threats and no one can disagree with that, surely.

"You know there was a time when we gave up on sabres or horses.

"You need to keep updating your defence policy and meeting the most pressing and most obvious needs."

Ms Griffith told BBC2's Newsnight: "Nobody has raised the issue of removing the Trident nuclear deterrent from our manifesto."

She pointedly added: "With all due respect, Emily is not the shadow defence secretary. I am."

Asked if Ms Thornberry was wrong, Ms Griffith said: "Indeed.

"Last year we looked at it, in particular, at the national policy forum and it was decided that we would keep the nuclear deterrent and that was reaffirmed at our conference in September."

Labour's candidate for the Cumbria constituency of Barrow and Furness, where the Trident shipyards are located, said Ms Thornberry's comments were "unfortunate" but would have no impact as Labour would not win the election.

Prominent Corbyn critic John Woodcock, who has previously said he could not support the Labour leader for prime minister, said Trident renewal had already passed the "point of no return".

He told BBC Radio 4's Today programme: "The policy on this is settled.

"There's a defence review at the start of every parliament.

"I think the Conservative government will do one when they return to office after June 8.

"This is a very unusual situation for the country to be in, but I have taken the decision to be honest and say that we know nationally what the result of this election is going to be.

"We know that Theresa May called this election because she's 20 points ahead in the polls and she's going to be Prime Minister after the election."

Ms Thornberry's comments would distract from Labour's efforts to exploit Conservative vulnerability on domestic issues such as the treatment of pensioners, warned Mr Woodcock.

"Labour is going to be in opposition and the important thing is that we have as strong an opposition as we can and we don't allow a Tory landslide because of all the other things on domestic policy where they will do damage," he said.

"I'm pleased to say I'm not the person who can explain what is in Emily Thornberry's mind at any particular moment.

"But it is unfortunate she said what she did because it creates confusion when in fact there is none about our policy, and we should be talking about the damage the Tories would do domestically."