The three most recent Liberal prime ministers have backed their successor Scott Morrison’s changes to make it much harder to sack a sitting prime minister.

The new rules, approved at a snap Liberal party room meeting on Monday evening, mean they cannot remove a sitting prime minister who has won an election unless they have a two-thirds majority.

Former prime minister John Howard, who famously described the Liberal leadership as a “gift of the party room”, said the events of the past five years had been enough to change his mind about the need for tougher rules.

READ MORE Turnbull tells Morrison to call an early election as Liberal infighting heats up

“They respond to that concern, but they also preserve the authority of the parliamentary party completely when it comes to choosing the leader,” Mr Howard, the longest-reigning ex-PM alive today, told reporters in Canberra.

He said the changes would offer a “reassurance of continuity” to the Australian people.

Earlier, Malcolm Turnbull was asked about the changes on his morning walk to catch a ferry in Sydney.

“I welcome the changes, I think it's a good change,” Mr Turnbull said.

“It will be well-received. How effective it is? Only time will tell,” he said.

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The rules do not apply to Liberal opposition leaders, who can still be rolled with the regular 50 per cent majority.

Scott Morrison is also outside the protection of the higher standard because he has not won an election as leader.

Mr Turnbull himself might still be prime minister if the rules had been in place in his time.

“Well, you know, you can’t live your life backwards,” he said.

ABC

Tony Abbott, who Mr Turnbull replaced in a leadership spill, was asked whether he wished the rules were in place when he was overthrown.

“That was then, this is now, a very sensible move from the prime minister and he's got my full support,” Mr Abbott said.

Federal Finance Minister Mathias Cormann says Australian voters could finally be confident the Liberal prime minister they elect will be the one who leads the party, after two political executions in three years.

"What we are making sure here is [ensuring] that people across Australia can have confidence if they elect Scott Morrison as prime minister at the next election, he will continue to be the prime minister all the way through the next term of parliament," Senator Cormann said.

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READ MORE Craig Kelly saved from preselection stoush despite Turnbull intervention

Prime ministers will stay put unless two-thirds of the federal party room support a change. The threshold is high and MPs expect it would be very rarely achieved.

"This has been the great anguish of the Australian people," Prime Minister Scott Morrison said.

"They're sick of it and we're sick of it and it has to stop. That's why we've put this rule in place."

The new leadership rules come after Mr Turnbull urged Mr Morrison to call an early election, while attacking the potential re-endorsement of conservative Liberal MP Craig Kelly as the "worst and weak" response.

AAP

Mr Turnbull said a snap poll soon after the summer break would be in the “best interests” of the party.

“It would be manifestly in the best interests and prospects of the government to go to the polls as soon as possible after the summer break,” he told ABC Radio on Monday morning.