A Labour MP has warned that Jeremy Corbyn’s pledge never to authorise the use of Britain’s nuclear weapons makes the prospect of a “grotesque horror of a nuclear holocaust” more likely.

John Woodcock, whose Barrow and Furness constituency is where much of the work for the new submarines will take place if MPs give the go ahead for the renewal of Trident next year, said Mr Corbyn’s comments were “unfortunate” and “concerning” for Britain’s national security.

He said that if Mr Corbyn took his current views into Downing Street, it would make the prospect of a nuclear war more likely.

187 countries don’t feel the need to have a nuclear weapon to protect their security, why should those five need it themselves? <p>Jeremy Corbyn</p>

Mr Woodcock’s comments came as an extraordinary row erupted between shadow cabinet members, with shadow defence secretary Maria Eagle questioning his ability to become Prime Minister by saying he would never press the nuclear button.

Asked earlier if he would ever be prepared to authorise the use of nuclear weapons if it came to it, after making clear his intention to push through plans for Labour to back unilateral disarmament in his keynote conference speech yesterday, Mr Corbyn said: “No. 187 countries don’t feel the need to have a nuclear weapon to protect their security, why should those five need it themselves?

“We are not in the era of the Cold War any more, it finished a long time ago.”

Mr Woodcock responded angrily and expressed sympathy for the majority in the shadow cabinet who were strongly in favour of renewing Trident.

“I think the unfortunate thing about what Jeremy Corbyn has said today that if that were the policy of a future prime minister it would make the grotesque horror of a nuclear holocaust more likely, not less because it would remove any utility for Britain’s independent nuclear weapons to act as a deterrent,” he told BBC News.

“The whole point of the UK and other nations within the Nato alliance having nuclear weapons is that they deter, they make less likely the possibility of nuclear war so it’s concerning from that point of view.”

He added: “I would imagine it’s dispiriting for the likes of Andy Burnham and Maria Eagle and many other members of the shadow cabinet who were asked to serve by Jeremy and in the case of Maria was given a specific responsibility for defence that the views and the reassurances that I guess they were given when they took those jobs have been treated in this way by what Jeremy said this morning.”

Ms Eagle, who has the job of overseeing Mr Corbyn’s “open dialogue” on whether to renew Trident, could not hide her discontent at the comments.

“I think it undermines to some degree our attempts to try and get a policy process going. As far as I’m concerned we start from the policy we have,” she told BBC Radio 4.

“I don’t think that, a potential Prime Minister answering that question like that, in the way in which he did, is helpful.”