Labor's new leader will be announced on October 13 after a ballot of the caucus and grassroots members of the party.
Two senior caucus members, Bill Shorten and Anthony Albanese, will contest the ballot.
But nominations will remain open until 5pm (AEST) on Thursday.
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The ALP national executive decided on Monday to open the grassroots ballot to all members who were financial as of September 7, rather than impose a limit on members who had been on the books for two years or more.
The members ballot will open on September 24 and close on October 9.
Caucus members will meet at 4pm (AEST) on October 10 to cast their ballots and the final result will be announced on October 13.
"This is a good thing for Australian democracy, a good thing for the Labor party, to invite so many more people to share with us the importantdecision about who should be our alternative prime minister leading our party over the next term," acting Labor leader and former treasurer Chris Bowen told reporters in Canberra on Monday.
It will be the first time the parliamentary leader of the ALP has been chosen with the help of members outside the caucus, who have a 50 per cent say in the matter.
Mr Bowen said there would be a series of events at which the leadership candidates would speak, some in public and some limited to ALP members.
Candidates would not use their parliamentary entitlements for campaigning purposes, but there would be funding arrangements in place through the ALP national executive.
Mr Bowen said there had been a strong surge in people wanting to join the ALP since the election, despite Labor losing government.
