Labour MPs hoping to replace Angela Rayner as the party’s deputy leader have until Thursday to secure the support of colleagues at Westminster.
The timetable for the contest has been set out by the party’s ruling National Executive Committee, with the result of the process set to be announced on October 25.
In the first stage, candidates have to secure nominations from 80 MPs – a fifth of the total on the Labour benches – by 5pm on Thursday.
Nominations open on Tuesday, with a hustings on Wednesday as part of the fast-tracked election process.
They will then have to secure the support of 5% of constituency parties or at least three affiliates – including at least two affiliated trade unions.
The ballot for candidates who clear the nomination hurdles will open on October 8 and close at noon on October 23, with the result announced on October 25.
Labour’s annual conference starts on September 28 and is likely to be used as a key moment in the campaign, potentially causing problems for Sir Keir Starmer as candidates set out rival visions for the party.
The successful candidate will replace Ms Rayner as deputy Labour leader but not as deputy prime minister, a position which has been handed to Justice Secretary David Lammy.
Home Secretary Shabana Mahmood has ruled herself out of the deputy leadership race after being tipped as a potential candidate.
She told broadcasters in London: “I’m the Home Secretary, so that is my job, and my top priority is securing our borders. I will not be running for deputy leader of the Labour Party.”
Former Cabinet minister Louise Haigh, who was championed as a potential candidate by Greater Manchester Mayor Andy Burnham, is also not thought to be planning to enter the contest.
But Foreign Affairs Committee chairwoman Dame Emily Thornberry has indicated she is thinking about a bid, but like both Sir Keir and Mr Lammy she represents a north London constituency which could count against her.
Former deputy leader and Labour veteran Baroness Harriet Harman said the role should be filled by a woman from outside London.
“I think that, in terms of extending the breadth of the leadership, it probably needs to be somebody from outside London and it definitely needs to be a woman,” she told BBC Radio 4’s Today.
“I don’t think we can have a male prime minister, a man as deputy prime minister and a male deputy leader of the party.
“We need somebody who is not a counterpoint to the leader, but is complementary to the leader, will broaden the reach of the leader and galvanise the party.”
The contest was triggered by Ms Rayner’s resignation following an ethics investigation which found she had breached the ministerial code over her underpayment of stamp duty on a seaside flat earlier this year.
Sir Keir has sought to draw a line under the scandal, completing a major Government reshuffle on Sunday night and telling his new-look Cabinet to “go up a gear” in delivering on Labour’s pledges.
But he now faces the prospect of a party conference overshadowed by manoeuvring for the deputy leadership role vacated by Ms Rayner, who was popular among the grassroots and seen as a bridge between No 10 and the wider party.
Meanwhile, Ms Rayner is facing Opposition pressure to reject a severance payment which ministers are entitled to when they leave Cabinet.
New Labour rules coming into force in October will allow the Prime Minister to deny a golden goodbye to any members of Government found to have committed a “serious breach” of the ministerial code.
But ministers have said that because Ms Rayner’s departure comes before the changes kick in, it is a decision for her whether or not she takes the payment, which could be as much as £16,876 under existing rules.
The Prime Minister’s official spokesman said: “It’s obviously right that we’ve changed the rules and are strengthening those rules, which will come into effect in October.
“But I’m not going to get into into individual cases.”
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