Labour’s new leader will be announced on April 4.
The party’s ruling executive has laid out the timetable for electing Jeremy Corbyn’s replacement.
From January 7, MPs and MEPs can nominate candidates.
Registered supporters will have to pay £25 to vote in the leadership election and can sign up in a 48-hour ballot which will be between January 14 and 16.
Voting opens on February 21 and closes on April 2 with the result announced two days later at a special conference.
Labour’s process means hopefuls have to get the required 22 signatures from MPs or MEPs and then they move on to seeking nominations from CLPs/unions, where they need backing of around 5% of either.
After the General Election result in December 2019, Mr Corbyn said he would stand aside for a new leader to be appointed.
So far, five MPs have put their names forward; Clive Lewis, Lisa Nandy, Jess Phillips, Sir Keir Starmer and Emily Thornberry.
Sir Keir Starmer is currently the favourite, with Rebecca Long Bailey in second.
Labour’s shadow Brexit Secretary, Sir Keir has also been Director of Public Prosecutions and head of the Crown Prosecution Service.
He was given a knighthood in 2014 for “services to law and criminal justice”.
He was elected as an MP in 2015 and said he didn’t stand in the last leadership battle because he said he didn’t have the experience.
A Labour spokesman said: “Our national executive committee has agreed the timetable and process for the leadership and deputy leadership elections. The ballot will run from 21 February to 2 April, with the results announced on Saturday 4 April.
“We are by far the largest political party in the UK with well over half a million members. We want as many of our members and supporters to take part, so it has been designed to be open, fair and democratic.”