How Labour's leadership contest works and what it means for Jeremy Corbyn

Everything we know about Labour's ballot rules now Angela Eagle has launched her challenge

Labour Party Leader Jeremy Corbyn attends anti-semitism inquiry findings at Savoy Place, on June 30 (Getty)

Members of Labour’s national executive will be silently cursing the people who drafted the current edition of the party rule book, for leaving a gap that threatens to embroil them in a nasty legal dispute.

In drafting the rules, Labour officials simply did not foresee a situation in which there would be a sitting leader fighting to hold onto his job having lost the confidence of so many of his MPs as Jeremy Corbyn has done.

Rule 4.2.ii of the Labour party rule book says that when an incumbent party leader faces a challenge “any nomination must be supported by 20 per cent of the Commons members of the PLP. Nominations not attaining this threshold shall be null and void.”

It does not spell out whether that applies to an incumbent leader - probably because the people who wrote never thought there would be an incumbent who would fight on when he could not count on the backing of one in five Labour MPs.

Neil Kinnock, the last sitting Labour leader to face a challenge, has absolutely no doubt that the rule means that Jeremy Corbyn would have to find 50 Labour MPs or MEPs to sign his nomination papers.

Jeremy Corbyn is equally sure that he does not need any nominations, because his status as the incumbent gives him an automatic right to be on the ballot paper. “I’m expecting to be on the ballot paper because the rules of the party indicate that the existing leader, if challenged, should be on the ballot paper,” He told the BBC’s Andrew Marr programme.

He and his supporters point out that party rules have changed since Lord Kinnock was challenged by the late Tony Benn in 1988.

Mr Corbyn also confirmed that he had “taken soundings” from lawyers about what the rules say. He hinted that if the executive decision went against him, he would go to court to fight for his right to be on the ballot paper. “I will challenge that if that is the view they take,” he said.

Labour’s General Secretary Iain McNicol is also reputed to have consulted a lawyer, and to have been told that Neil Kinnock’s reading of the rule book is the correct one.