Libs strike One Nation deal

"The Nationals WA have a strong policy platform that has garnered significant support from individuals, businesses and communities from all corners of our State," Mr Grylls said.

"While some political parties believe they own or influence preferences - we believe this shows great disrespect to voters."

Mr Grylls seemed unperturbed about the arrangement, stating "elections were not won on preferences, but on primary votes".

"The people of West Australia will always vote with their hearts and minds, and won't be told how to vote by a piece of paper resulting from a backroom deal."

The Liberals signed the deal with One Nation this week, giving preference to the Pauline Hanson party above the Nationals in the Upper House country regions, breaking the Nationals-Liberals alliance.

In return One Nation will list the Liberals above Labor in all Lower House seats it is contesting.

Mr Grylls confirmed his party had wanted a direct preference deal with the Liberals to continue building on its "strong record of achievement".

He said the deal with One Nation was made despite comments from Premier Colin Barnett otherwise.

"As alliance partners in government for the past eight years The Nationals WA have always acted in the best interests of our constituents, even if this meant taking a different position to the Liberal Party," Mr Grylls said.

"While we have had our differences with the Liberal Party, we have delivered strong and stable government for the people of WA throughout this time.

"The Nationals WA remain focused on representing the regions, defending our flagship Royalties for Regions policy and delivering a new revenue source to get the State back on track."

Mr Grylls said other parties that focused on preference deals would be judged harshly on polling day.

"The Nationals WA have always prioritised people over politics and our team is working hard to address the issues, concerns and priorities of the West Australian community," he said.

"The Nationals WA is an independent political party focused on delivering the best possible outcome for regional West Australians."

Federal Nationals leader Barnaby Joyce said Mr Barnett had increased the risk of losing the election because of the deal.

"Colin Barnett has been around the political game a long while and should seriously consider whether he thinks this is a good idea," he told Financial Review reporters in Canberra this month.

Mr Joyce said Liberal-National governments had a track record of success.

Mr Barnett defended the deal, stating One Nation was a different party from what it was in the 1990s.

"We are not endorsing One Nation candidates or policies in any sense - it is basically a mathematical exercise," Mr Barnett said.

"The objective is to maximise the Liberal party votes, particularly in the Lower House where government is determined."

Mr Barnett said parliament would be complicated after the election.

"There will be Liberal Upper House members, Labor, Greens probably, One Nation, and Independents - who knows?" he said.

"The critical preferences are in the Lower House."

WA Labor leader Mark McGowan said the Nationals, Liberals and One Nation were "falling apart".

"This was a dirty deal, done dirt cheap in order to save Colin Barnett," Mr McGowan said.

"(It's a deal) to sell off Western Power and I am telling all West Australians not to fall for it.

"The only choice for stability, leadership and competence in WA is WA Labor.

"We are at a serious point in our State's life, we need stability, leadership and competence.

"The Nationals, Liberals and One Nation are an arguing rabble."

Mr McGowan said the deal joined two parties that had polar-opposite ideas on policies.

"What it shows is, the Liberals will do anything to hold onto power, including joining with a party that says it won't support its policies," he said.

"The only party that you can rely upon not to sell Western Power, to preference local workers over foreign workers is WA Labor.

"This set of events shows the Nationals, Liberals and One Nation party are all in it together, they are not fit to be in government."

Mr Barnett defended the move and said the government had clear plans to sell 51 per cent of Western Power to pay off government debt.

"As far as One Nation, if they have members of parliament elected to the Upper House, which is probable, they can vote on legislation," Mr Barnett said.

"If the Liberal government returns we will bring on legislation for part privatisation of Western Power - all 36 members have to vote in the Upper House."

Mr McGowan said the deal was made in order to save Mr Barnett.

"If you don't like that, don't vote for the Liberals, don't vote One Nation," he said.

"It is clear there is a mess on the other side of politics."