Mr Corbyn was asked in an interview with BBC Radio 4’s Today programme whether he would ever push the nuclear button.
“No,” he replied. “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.”
The statement comes as the Labour party debates whether or not to retain its policy of renewing the Trident nuclear weapons system, which is up for renewal soon.
The Labour leadership narrowly avoided a vote on what its policy should be on Trident at party conference in Brighton this week after delegates prioritised other issues for debate.
Critics of Trident say it would cost around £100bn, would kill civilians en masse if ever used, and is not an effective.
The SNP, which also opposes Trident renewal, says much of the money could be invested in conventional forces that would be a more effective defence against the types of threats faced in 2015.
Mr Corbyn says Britain has obligations under the international nuclear proliferation treaty and should scrap Trident as a step towards a nuclear weapons free world.
Proponents of renewing Trident say the weapons act as a deterrent to missile attack from potential countries.
Mr Corbyn’s statement means that the system would effectively be useless as a deterrent when he was prime minister because other countries would know it would never be used.
The UK is one of only nine countries in the world to have nuclear weapons. The only other EU country to maintain a nuclear arsenal is France.
The Conservatives claim Mr Corbyn is a “threat to national security” because of his stance on defence and foreign policy.Reuse content