Labor has left the door open for the caucus to reverse Kevin Rudd's rule that makes it nearly impossible for the party's elected leader to be toppled in a midnight coup.

The Australian Labor Party's draft national constitution, published on its website, includes changes made to the way the leader is elected - by an equally weighted ballot of caucus and party members.

Former prime minister Kevin Rudd and Julia Gillard in an infamous appearance together after she replaced him as prime minister. Credit:Andrew Meares

But significantly, it does not include the caucus-approved rule that the prime minister can only be removed if 75 per cent of MPs agree to force a ballot. This is lower - 60 per cent of caucus - for an opposition leader.

The changes, aimed at preventing a sitting prime minister from being suddenly toppled, were introduced by former leader Kevin Rudd after his political resurrection and signed off at a special caucus meeting in Balmain in July, 2013.