THE WA Liberal deal with Pauline Hanson's One Nation has been given the blessing of former prime minister John Howard, despite his 2001 edict it must be placed last on his party's how-to-vote cards.

Adding star power to the Liberal election campaign in Perth on Thursday, the nation's second longest serving prime minister said the WA division made a "very sensible, pragmatic decision" to cut a deal with the right-wing party.

"I fully understand why the WA Liberal party has taken the decision," he told reporters at a shopping centre in the seat of Southern River on Thursday, when he received almost entirely positive responses from voters and children.

Mr Howard said One Nation had morphed into a different beast since his 2001 instructions, although he still didn't agree with everything it espoused.

"Everyone changes in 16 years," he said.

"Trying to understand that decision and decisions that were taken by various iterations of the Liberal party 15 or 16 years ago is ridiculous.

"This is a different set of circumstances.

"I think it's entirely sensible that the party has done what's it's done."

The Greens were the only ones who hadn't changed, he said, and advocating dismantling the US alliance illustrated the party's continuing extremism.

"The idea that people would see the current One Nation party as more extreme than the Greens is ridiculous," Mr Howard said.

"And who's playing footsie with the Greens - the Australian Labor Party."

His comments came after WA Premier Colin Barnett refused to be drawn on whether the Liberals were morally wrong to seal the deal, snubbing alliance partners the Nationals, which retaliated with its preferences.

Mr Barnett admitted some of the headline-grabbing views of candidates were abhorrent but said it was a numbers game and he had an election to win.

The latest comments from One Nation hopefuls dogging the party reportedly came from the now-deactivated Twitter account of Richard Eldridge, who is contesting an upper house seat in Perth's South Metropolitan region.

In the posts, Mr Eldridge, a real estate agent, advocated killing Indonesian journalists and also attacked the gay community, black people and Muslims.

Old social media posts are also haunting Michelle Myers, who was nominated for the newly-created seat of Bateman.

On Facebook last year, she said the gay community used Nazi-style mind control to get people to support same-sex marriage and has recently been protesting against abortion outside a reproductive health clinic in Midland, where women also get fertility treatment.

"In absolutely no way do I endorse the policies or candidates of One Nation," Mr Barnett told reporters.

"I find some of those comments absolutely abhorrent.

"I'm not going to be defending One Nation - go and talk to Pauline."