West Australian Premier Colin Barnett says he's ready to rumble with his opponent Mark McGowan, who he claims doesn't have what it takes to cut through in Canberra.

Ahead of the only leaders debate of the state election campaign on Wednesday, Mr Barnett defended his two-term government's track record and took a few swipes at the Labor leader, saying he would be a puppet of the unions.

"I've seen people far more experienced in the Labor party than Mark McGowan simply being told what to do at COAG by Kevin Rudd, Julia Gillard and others," Mr Barnett told reporters.

"So don't for a moment think Mark McGowan is his own man. He'll be answerable to the unions in WA and he'll be totally answerable to Bill Shorten in Canberra."

Mr McGowan returned fire with a sweeping statement that Mr Barnett had made a mess of WA's economy, was going to flog off Western Power "and then he's going to retire".

The premier has long maintained he won't serve a full third term if re-elected, but recently added he'd serve most of four years, with his successor widely believed to be Deputy Premier Liza Harvey.

"I'm going to be there for the long haul if I'm successful at the election," Mr McGowan told reporters.

Mr Barnett was reminded by the press of his much-lampooned Kimberley canal plan, mentioned in the 2005 debate, and his 2013 pledge to keep electricity price increases at or around the inflation rate.

He later qualified that wasn't a full-term promise and was only for the first year.

Mr Barnett maintains the Liberals had no choice but to increase power prices to fix problems it had inherited, and singled out the MAX light rail plan as the only pledge that hadn't been honoured.

"With the exception of that, I have delivered pretty well everything I've promised," he said.

The economy was turning the corner, but if voters went back to a Labor government, the state would "grind to a halt", he said.

Both leaders fielded questions about pamphlets distributed at mosques by a group of prominent Islamic leaders, who advised Muslims to vote for the Greens to counter the expected influence of Pauline Hanson's One Nation.

The imams said a Labor win - and as many Greens as possible in parliament - would be an ideal state election outcome.

But Labor, which will get Greens preferences, should also be sent a message for "flirting" with the idea of a preference deal with One Nation, the pamphlet says.

Mr McGowan said he wasn't too worried about the how-to-vote message while Mr Barnett said the Liberal deal with the right-wing party was "a mathematical necessity".

"I hope people will think about their vote and not just simply jump to a point of view, which I don't think is fair," he said.

"I would simply say to the imams, and particularly to any Muslim people, 'judge us on how you find Western Australia, judge us on how this government has made you feel welcome'."