SYDNEY - Australian Prime Minister Malcolm Turnbull on Sunday (April 8) crossed an ominous line that could spell the end of his leadership.

When he toppled former Prime Minister Tony Abbott in 2015, Mr Turnbull justified the move by noting that Mr Abbott had trailed the Labor opposition party in 30 consecutive Newspoll opinion surveys.

On Sunday, he trailed Labor for the 30th time in the highly anticipated survey, crossing the leadership threshold he now wishes he had never set.

It is a self-inflicted tipping point that is being keenly watched in Canberra, not least by Mr Turnbull's political opponents.

The milestone could trigger yet another round of leadership chaos in Australia - a nation that has had five changes of leader since 2007 and has been nicknamed "the coup capital of the world".

Attempting to head off the inevitable bad news and the ensuing leadership speculation, Mr Turnbull has insisted that his move against Mr Abbott was not motivated solely by the ruling Liberal-National Coalition's run of bad polls.

"I certainly wish I hadn't referred to 30 Newspolls because, while it was not telling anybody anything they didn't know, it certainly is proving a distraction from the real issues we're dealing with today," he told Fairfax Media on Saturday.

Asked if he would call a leadership vote if he recorded a 30th Newspoll loss, he said: "No. What the Australian people want me to do is to get on with delivering and governing, and that's what we're doing."

After ousting Mr Abbott, Mr Turnbull, a former investment banker and self-made millionaire, won a general election in 2016 with a only razor-thin margin that damaged his standing within the party.

His public popularity plunged as he abandoned his well-known progressive approach to issues such as climate change, same-sex marriage and becoming a republic. This was widely seen as an attempt to placate the conservative wing of the Liberal party, which has long distrusted his progressive views.

Mr Turnbull has also suffered from persistent criticisms by his long-time political foe, Mr Abbott, who remains an MP.

Few believe that Mr Abbott - a staunch conservative who is publicly unpopular - could achieve a comeback as leader. However, his regular criticisms of the government's policies on issues such as energy and taxation have severely undermined Mr Turnbull's position.

Mr Abbott made no attempt on Sunday to hide his continued anger at his ousting or his dim view of Mr Turnbull's leadership. He said that Mr Turnbull's decision to set 30 Newspoll losses as a benchmark was "not fair".

"As for that particular metric, that was not my metric and it is for others to explain the rhyme or the reason in it," he told The Sunday Telegraph.

"Life is not fair. We know that."

Analysts believe Mr Turnbull appears to have little chance of winning the next election, which is due to be held by next year.

Some have suggested he should resign or call a leadership ballot to reassert his authority. However, despite speculation about possible leadership contenders such as Home Affairs Minister Peter Dutton, Foreign Affairs Minister Julie Bishop or even Mr Abbott, there is no clear alternative to Mr Turnbull.

The last Australian PM to remain in office without being toppled was Mr John Howard, a Liberal who led from 1996 to 2007.

Mr Howard called for the party to unite behind Mr Turnbull and insisted that the Coalition could defeat Labor leader Bill Shorten at the next election.

He said Mr Turnbull needed to inspire and lead but the party's MPs also had an obligation to work together. "I don't find any evidence in the party of people wanting a change of leader," he told ABC News on Thursday.

"We have done that and we still have an electoral challenge... Malcolm Turnbull has got to give the lead, that can't be disputed, but he is not the only person who has got a responsibility."

But the Newspoll survey, published in The Australian newspaper, has only led to increased leadership speculation and is making it more difficult for Mr Turnbull to finally reverse his dismal run of polls.

To improve his standing, Mr Turnbull needs to switch the conversation away from Liberal party infighting towards bread-and-butter issues such as jobs and the economy.

His decision to set 30 poor poll results as a test of leadership, however, will mean that Canberra will be talking about little else.