Evangelical Christian Scott Morrison, who emerged as prime minister after a ruling party bun fight, is a key architect of Australia's controversial "stop the boats" policy to halt the arrival of seaborne asylum-seekers.

Morrison, an ambitious man who has always dreamed of the top job, snatched the leadership from the hands of hardline conservatives who had engineered the ouster of incumbent moderate Malcolm Turnbull.

Morrison, who was immigration minister before becoming treasurer, was reportedly quietly canvassing support among his colleagues as Turnbull feuded with his rivals during the week.

The 50-year-old's stealth candidacy reflected aspirations he has had since he entered parliament in 2007, representing the Sydney seat of Cook - the site of Australia's last race riots in 2005.

"I look forward to it. I relish it," he said after rising to the country's highest political role.

The son of a policeman, Morrison - known as "ScoMo" - becomes Australia's seventh prime minister in 11 years, replacing a man who became the latest in a long line of leaders knifed in the back by their allies.

He built his reputation in the party as a tough but effective operator when he took on the immigration portfolio from 2013-14, implementing the controversial "Operation Sovereign Borders" to stop asylum-seekers arriving in Australia by boat.

Protesters take to the streets of Melbourne in 2014

They were either sent back to where they had come from or transferred to remote Pacific island camps, a policy roundly criticised by the United Nations and rights groups.

A defiant Morrison stared down his critics and enforced a veil of secrecy around the military operations to turn back boats, sometimes to countries with poor human rights records.

As doctors and advocates slammed the conditions in the camps on Manus Island in Papua New Guinea and on Nauru, where some asylum-seekers were held for several years, Morrison celebrated the fall in the number of arrivals.

He stressed that the policy had stopped the tide of boats and prevented people from drowning at sea when they undertook the long, treacherous journey to Australia.

Even so, critics questioned how the man in charge reconciled his worn-on-the-sleeve Christian faith with his uncompromising immigration stance.

Greens leader Richard Di Natale, who has pleaded for politicians to consider the plight of asylum-seeker children held on Nauru, said today that Morrison's policy had left a "toxic legacy of cruelty to vulnerable people".

'Family and faith'

Born 13 May 1968 in the beachside Sydney suburb of Bronte, Scott John Morrison was the younger of two sons, whose parents ran church youth programmes.

Morrison himself was an active church member, and met his wife Jenny as a young teenager through the church. The pair married when he was 21.

It took 18 years and multiple rounds of IVF before the first of two children was born, and Morrison dedicated his maiden parliamentary speech to his daughter Abbey Rose.

Morrison worked in the tourism sector at home and in New Zealand before being selected to contest the seat of Cook in 2007.

Scott Morrison is hugged by his daughter after a parliamentary event in 2014

He credited his win to the "most significant influences on my life - my family and my faith".

After serving as shadow immigration minister, Morrison moved straight into the government job when the Liberal party took power in 2013.

A short stint in the social services portfolio followed, before he took over the treasury when Turnbull became leader in September 2015.

Morrison presided over Australia's economy as the government sought to return the budget to surplus and simultaneously cut personal income and small business taxes.

On social issues, Morrison has stood to the right of the more moderate Turnbull, and opposed the legalisation of same-sex marriage last year.

But he has also tried to soften his image, appearing on a cooking-with-politicians series that airs on national broadcaster ABC.