The Liberal candidate for the Canning byelection, Andrew Hastie, has refused to be drawn on whether he shares his father’s views on creationism, saying his religious views are irrelevant to voters, and that “people are sick of this crap”.

Asked eight times at a media conference in Armadale on Thursday whether he believed in creationism, Hastie at first skirted the question, which he claimed was irrelevant to the 19 September poll, because: “There’s no religious test in this country for public office.”

“Like many Australians, I have a Christian faith, which presupposes the existence of a God,” he said.

“The belief that there is a God endows every person with dignity and it inspires me to treat people with equality, and so my faith has taught me to love others, not judge others.”

Hastie had called the media conference to announce he would push for harsher mandatory minimum sentences for methamphetamine dealers who sell to people under 18, or manufacturers who “endanger” children” – a state government issue, so his promise was to lobby the Barnett government. Tackling methamphetamine use has already been announced as a major focus for the Liberal campaign.

But it soon became derailed by questions about his views on the refugee response – the former SAS officer served three tours in Afghanistan, was an adviser to the Abbott government on Operation Sovereign Borders, and said: “I saw what good policy looks like on the ground, and now that we have transitioned to an orderly process for receiving refugees, I welcome 12,000 more” – and questions about his religious beliefs.

Andrew Hastie addressing what he said was an unacceptable media focus on his family last Friday. Link to video

He shrugged off suggestions his religious views could one day become very relevant to public policy if he became, say, science minister, saying: “No, look, look … I’m interested in the people of Canning, I haven’t done science since year 12 at high school and I’m not interested in talking about curriculum or anything else, I’m interested in talking about Canning and public policy solutions for them.”

When pressed again, he said: “I believe there was a God, I believe he was the first mover,” adding that there was “plenty of disagreement within Christianity itself about the specifics of creation, of theistic evolution”, before directing journalists to look up John Dickson, the founding director of the Centre for Public Christianity if they wanted a theological debate.

He then became more abrupt, saying to one journalist: “Damien, Damien, you’re not hearing me mate. I’m talking about public policy. You’re trying to drag us – people are sick of this crap.

“People are sick of trying to drag petty issues into public policy issues. People in Canning don’t care.”

Hastie last week made a statement in defence of his father, Peter Hastie, a presbyterian pastor and principal of the Presbyterian Theological College who has written articles in defence of creationism, and his wife, Ruth, both of whom he said had been the subject of “unacceptable” questions from the media.

He has previously identified himself as an Anglican and one of three candidates in the crucial byelection, which was triggered by the sudden death of sitting Liberal MP Don Randall, to have publicly voiced their opposition to marriage equality. It’s a stance that has won him the preferences of the Australian Christians party, who told the ABC on Monday that they would “reward” the 32-year-old for his “correct and conservative view on traditional marriage”.

Asked on Thursday how that opposition to marriage equality aligned with his stated desire to treat all people equally, Hastie said he was advocating for a popular vote, or plebiscite, on the issue and would support the result of that vote.

“There’s no bogeyman, I’m advocating for a popular vote, and if the people want it, then I am obligated to do that,” he said.

Hastie said he hoped voters in Canning would support the Abbott government’s decision to accept 12,000 extra refugees from Syria and Iraq, saying: “If I was a parent or a mother or a child living in Syria or Iraq I would certainly be fleeing myself.”

“As you’re aware, I’ve served in the Middle East, I’ve looked at Isis in detail, I’ve watched pretty much all of their propaganda videos, I know how evil they are,” he said, before adding his support for Australia to join US-led against Syria: “the Islamic State must be defeated, and at this point in time ... military force is one way that they need to be stopped.”

The changes to state law proposed by Hastie would see the minimum mandatory sentence for people who sell methamphetamine to children increased to 12 months’ jail and extended to first-time offenders, and a two-year mandatory minimum jail term applied to people who “endanger children” in the manufacture of methamphetamine. Currently, people who sell or supply a prohibited drug to people under 18 in Western Australia face a mandatory six-month sentence on their second conviction.

WA already has overcrowded jails, in part from its mandatory sentencing policies. Hastie referred questions about how his proposal would affect prison overcrowding to the state corrections minister, Joe Francis.

Matt Keogh – the Labor candidate for Canning who has been vocal in his opposition to mandatory sentences both as head of the Law Society of WA and in his statements on the campaign trail – described the announcement as a diversionary tactic.

“This is a quite clear attempt at distraction from the fact that the only investment Mr Abbott has been prepared to make in Canning is an investment in advertising to try and save his own job,” he said.

Speaking at a media conference in Mandurah, about 45 minutes from Armadale in the seat of Canning, on Thursday, Keogh invoked his experience as a federal prosecutor with the office of the Commonwealth Director of Public Prosecutions, and said: “I understand what works.”

“Seven years of the Barnett government so far, with their approach to crime, has lead to WA becoming the ice capital of Australia,” he said.

The federal shadow treasurer, Chris Bowen, was in Mandurah to campaign with Keogh, taking leave of a parliamentary sitting day because “today is the day that it suited the campaign to come”.

He stepped in to support Keogh’s credentials, saying: “He’s actually put drug dealers behind bars.”

“As I understand it, the current maximum penalty is 25 years,” he said. “If Mr Hastie wants to talk to the state government, his Liberal colleagues in the state government about two-year sentences, that’s a matter for him.”