Griffith University emeritus professor Patrick Weller said Australia is too trigger happy in replacing prime ministers, which has led to a revolving door of political leadership.

While other countries with a Westminster system such as the UK, New Zealand and Canada can remove a prime minister in a leadership ballot, more processes are in place to ensure it is difficult to do so.

"In Australia, leaders are kicked out on the spot," Professor Weller said.

"While Australia has more accountability, the danger is you can pull the trigger too easily. In other countries with similar systems, leaders are elected through a party convention and only removed by a party convention."

In the past eight years, Australia's seen eight leadership spills with four being successful, requiring just a simple majority to change leader.

In the UK, there have only been three spills in the past three decades, the last being against Conservative prime minister John Major in 1995, which was unsuccessful.

To have a leadership contest in Britain, Professor Weller said more requirements are needed to challenge.

"You need a signed petition of 15 per cent of the party, which then triggers a no confidence vote. If the vote fails, the leader can't be challenged again for another 12 months," he said.

"Theresa May is much safer than Malcolm Turnbull was because of different mechanisms in place."

In the UK's Labor Party, leaders are voted for by all party members.

"The broader the electorate is in choosing a leader, the safer they are," Professor Weller said.

By contrast in Canada, leaders can be elected through conventions, which are only triggered through the incumbent resigning.

While it may lead to more stable leadership and less spill motions, Professor Weller said it can lead to larger electoral defeats.

Canada's Progressive Conservative Party slumped to record lows in the polls before the 1993 election, causing them to go from holding 156 seats to just two.

"It's possible in Canada when a leader has lost the support of the party to have support run into the ground before a leader is prepared to move, and they can take a shelling in the polls," he said.

"Canadians make it too hard, Australians make it too easy."

New Zealand's system to replace leaders is similar to Australia's, but has only seen one instance of a sitting Prime Minister being challenged for the leadership in 1988.

While a simple majority is needed to roll a sitting leader across the ditch, Professor Weller said long-serving prime ministers such as Helen Clark and John Key made spills less likely.

Senior lecturer in politics at Monash University Nick Economou said New Zealand's parliament, which only contains a House of Representatives, make it more stable compared to Australia.

"New Zealand has a unitary system of government, and it doesn't have powerful players or an upper house frustrating the process," Mr Economou said.

"There is something really inherently volatile with Australian national politics, short-term prime ministerships are the norm, rather than the exception."

Only 12 of Australia's 30 Prime Ministers have served a full term in the role, and Mr Economou said changing leaders mid-term is just part of Australia's political system.

The political lecturer said the increase in leadership spills over the past decade can be attributed to two people.

"You can reduce the problem down to both Kevin Rudd and Malcolm Turnbull, both were very odd characters and were never fully embraced by their party," he said.

"Australia had two really different characters dragging down other people with them and leaving mayhem in their wake."