WA Premier Colin Barnett has again conceded winning a third term is a tough ask after fresh polling showed a widening lead by Labor and mounting support for One Nation.

The latest Newspoll shows the opposition has increased its lead over the Liberal-National government to 54 per cent in two-party preferred terms.

Mr Barnett's approval rating was higher than the previous Newspoll but lower than around the same time last year, with 32 per cent of respondents saying they were satisfied with his performance.

But he said he wasn't a "pop star" and never set out to be one.

"I think I have been a very successful, stable premier," he told reporters.

"If you want a pop star, that's not me. Not Mark McGowan either - he's boring."

The opposition leader said he was focused on policies and plans, not polls.

"Polls come and go. You don't ever take anything for granted," Mr McGowan said.

"It's a long way to the election.

"A lot of things will happen in the meantime. The government will throw the kitchen sink at it."

Mr McGowan didn't have much time to bask in the afterglow of good polling if he'd been inclined to, pressed to respond to claims by One Nation's party leader Colin Tincknell that Labor had made an approach about preferences.

"I didn't expect Mark McGowan to come knocking ... but they have. That happened yesterday," Mr Tincknell told ABC radio.

Mr McGowan said he had never met or spoken to Mr Tincknell.

"I wouldn't know him if he came up and tapped me on the shoulder," he said.

When asked if representatives from Labor had been in touch with One Nation, Mr McGowan would only say it was hard for members of various parties to avoid meeting each other at industry briefings.

"Not a big state - people run into each other."

Mr Barnett was also asked whether the Liberals had met One Nation officials, responding he was not involved with preferences.

The premier said he'd never met Pauline Hanson or even spoke to her, and doubted he would.

After One Nation's share of the statewide primary vote in the Newspoll soared from three per cent to 13 per cent, Mr Barnett said there was a lot of fascination with minor parties but hopefully voters would scrutinise policies and candidates as the election rolled on.

As the Nationals launched their campaign in Bunbury in the state's South West, leader Brendon Grylls drew chuckles for his reflections on One Nation.

"Supporting One Nation is a bit like buying a Chiko roll ... you take a bite of it, you're disappointed, and then you end up regretting it for the next couple of days," he said.

Mr Barnett was forced to vehemently rule out agreeing to support Mr Grylls' contentious mining tax after a media report suggested he would cave in to the Pilbara MP's will but he also confirmed the Nationals would get Liberal preferences as usual.