Former WA Premier Colin Barnett quits politics after 27 years

Mr Barnett said there were two types of politicians: those that played it safe and those that stood up and made tough decisions.

He wanted to be remembered as the latter.

"I hope I am remembered not only as a long-serving premier, but also as one who gave it his best shot," Mr Barnett said.

"I hope I am remembered as someone who behaved with honesty and integrity."

Mr Barnett made the announcement on ABC Radio on Friday morning, and will finish off his time as a member of parliament on Australia Day.

He joked about being back on the airwaves after a quiet time following the election defeat to a Mark McGowan-led Labor.

"A moment of relevance," he said.

The announcement comes nine months after the Liberal Party's landslide defeat in the WA State election.

Mr Barnett was re-elected as the member of Cottesloe, and he said he felt an obligation to see out the rest of the year as a backbencher.

"I am not the sort of person to cut and run and I felt an obligation after the election, as harsh as the Liberal defeat was, I was going back to parliament and face the music," he said.

"I felt very much like the elephant in the room.

"I have no regrets. It is just time to move on."

A by-election will be held for the blue-ribbon seat of Cottesloe following Mr Barnett's departure.

Senior lawyer Emma Roberts has emerged as a front-runner for the WA Liberal Party's pre-selection.

Ms Roberts recently met with Mr Barnett to discuss the role, and on Friday, Mr Barnett said she would be a competent replacement.

"But there will be other highly competent people," he said.

"If I anoint anyone it would be the kiss of death."

Only four people have served as WA premier for longer than Mr Barnett.

Prior to serving as premier, Mr Barnett was deputy Liberal leader and a senior minister in the Court government from 1993 to 2001.

In his time as premier, from 2008 to 2017, the state saw rapid growth in the mining industry before slipping into an economic downturn in later years.

"I know I am seen as an economic guy," Mr Barnett said.

"Hopefully it will be remembered that I was also involved in social and education policies, building hospitals, caring for people with disabilities and rebuilding the City of Perth.

"Perth had fallen a long way behind other Australian cities."

Mr Barnett's Liberal-National alliance government invested heavily in infrastructure, spending billions on new hospitals across the state.

His government also focused on big capital works to change the face of the city such as Perth Stadium, Elizabeth Quay and the City Link projects.

At 67 years of age, Mr Barnett said he had enjoyed a long career and, despite becoming known as 'The Emperor' during his long reign as WA leader, he insisted he was not pre-occupied with his legacy.

He had been frustrated at being perceived as a leader who looked after big projects but not much else.

"I am genuinely not about legacies," he said.

Mr Barnett said he was "satisfied in my own heart and soul" about the changes his government had made in all areas.

But opponents criticised him for the multi-billion-dollar deficit left behind after he left office.

Mr Barnett said the pressure of public life was a heavy burden to bear.

"Politics can take a toll. You are in a very public position," he said.

"It was only more recently that my boys said 'you don't know how tough it was for us at school when you were in a controversial situation'."

The Cottesloe MLA recognised that most political careers ended in tears, and abruptly.

Mr Barnett admitted his second term had been a very turbulent time, with big issues to deal with such as the unsuccessful shark cull during which the wrong type of shark was caught, and the collapse of the state's GST revenue.

He understood many people thought he overstayed his welcome as Liberal leader but now life had changed dramatically.

"I walk down the street now and people look at me - who is that guy?" he said.

"Politics can be quite selfish. I don't think I'm a selfish person, but the role is ... now I'm back to being just a regular person."

Mr Barnett placed an advertisement in his electorate's local newspaper on Friday, thanking voters for their support.

He said he would focus on local matters from now on.

"I won't have a public role but I will certainly be doing some things. I think I have one more mini-career in me," he said.

Former WA premier Colin Barnett thanks his supporters in the Subi Post - expected to announce today that he's leaving politics after nearly three decades.

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