Labour leadership hopeful Owen Smith made an explosive commitment this morning (20 July) as part of his campaign to dethrone Jeremy Corbyn. The Pontypridd MP said he would be willing to press the so-called "nuclear button" even if it meant hundreds of thousands of innocent people would die.

Smith made the vow on ITV's Good Morning Britain after Theresa May made the same pledge during a debate in the House of Commons on Monday over the renewal of Trident. MPs voted overwhelmingly 472 to 117 to upgrade the continuous at-sea deterrent, with Corbyn being among just 47 Labour MPs who opposed the £41bn ($53bn) Successor Programme.

Smith, a former member of the Campaign for Nuclear Disarmament (CND), attacked Corbyn over the issue ahead of the mammoth six-hour-long debate. "I was a teenager when I was a member of the CND and I have long since grown up and I now know that I don't think we can afford to divest ourselves of nuclear weapons right now," he told Sky News.

The former journalist is now the sole challenger to Corbyn, a lifelong unilateralist who has promised to push the "nuclear button" if he becomes prime minister, after Angela Eagle dropped out of the contest last night and threw her support behind Smith.

Eagle's move means the "soft left" vote of Labour is no longer split and Smith's name is easily expected to be on the leadership ballot, which requires 51 nominations from Labour MPs and MEPs.

However, a YouGov poll for The Times, of more than 1,000 Labour members between 15 and 18 July, put Smith on just 15%, with Eagle on 21% and Corbyn on 54%.

The left-wing leader, who secured almost 60% of the vote in the party's 2015 contest, is automatically on the ballot after a decision from Labour's National Executive Committee (NEC).

The ruling body also agreed that registered supporters could have a say in the election by paying £25 to the party, otherwise affiliated supporters and members will only be eligible to vote if they joined Labour on or before 12 January. The winner of the leadership contest will be announced in Liverpool on 24 September.