WA Premier Colin Barnett has sought to defend the Liberals' preference deal with One Nation by claiming Pauline Hanson's party holds less extreme views now than it did two decades ago.

Mr Barnett said the current party was "not the One Nation party of the late 90s", as the fallout of the preference deal struck by the Liberals continues.

The Liberals have agreed to direct preferences to One Nation ahead of the Nationals in Upper House regional electorates, while also putting it high on its voting ticket in metropolitan seats.

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But Mr Barnett's Government has faced criticism for the arrangement, particularly due to One Nation's policies around race issues.

Ms Hanson used her maiden speech as a senator last year to call for a Muslim immigration ban, and also wants wearing a burka in public to be outlawed.

But Mr Barnett insisted One Nation was less extreme than it used to be.

"I think some of the policies in the 90s were quite extreme and there was a very strong racial component to policies," he said.

"That is not something that I or the Liberal Party could ever accept."

Asked how he reconciled that view with the proposed burka ban, Mr Barnett said he did not think that was a "racial policy".

'You are always in control'

Questions have been raised about how much the Liberal Party will benefit from the preference deal, amid a backlash from One Nation candidates.

Numerous One Nation candidates are upset by the deal and some have even threatened to print their own how-to-vote cards, because they did not wish to direct preferences to the Liberals.

One Nation's WA leader Colin Tincknell even took to social media with posts telling voters they were "always in control" of where their preferences went.

But Mr Barnett said the deal would help to maximise the Liberal Party's vote.

"I am not part of One Nation's campaign at all and I am not interested," he said.

Nationals backlash begins

Meanwhile, the National Party has made the surprise decision to preference a sitting Greens MP over Liberal and Agriculture Minister Mark Lewis.

In the Mining and Pastoral and South West Upper House regions, the Nationals have decided to direct preferences to the Greens ahead of the second and third Liberal candidates.

In both regions, the top Liberal candidate is ahead of the Greens, but the left-wing party appears ahead of the remaining Liberals on the Nationals' group voting ticket.

In the Mining and Pastoral Region, that means National preferences will go to Greens MP Robin Chapple ahead of Mr Lewis.