A Liberal MP has warned the racism and ignorance embodied by One Nation leader Pauline Hanson could have tragic consequences for Australia, calling on his fellow politicians to explicitly reject her views.

Senator Hanson’s incendiary first speech in the upper house on Wednesday – in which she said Australia was in danger of being “swamped” by Muslims, called for a ban on further Muslim migration and declared multiculturalism had failed – sparked widespread condemnation.

But while a number of Turnbull government MPs said they thought Senator Hanson’s views were wrong, most were treading carefully given the Coalition needs One Nation’s votes to help pass its legislation.

However in an impassioned speech in Canberra, John Alexander – the member for the heavily multicultural Sydney seat of Bennelong – has gone much further, calling Senator Hanson’s speech “abhorrent”.

“I subscribe to the Voltairean principle of respecting people’s right to say things that I disagree with. But when that speech uses broad-brush strokes to demonise an entire religion and all the observers of that religion it must be called out for what it is – it’s racism, it’s discrimination,” he said in a little-seen speech in Parliament’s Federation Chamber.

The former tennis champion also took aim at Ms Hanson for claiming to know more about Islam than the people who practice it: “This must be called out for what it is – ignorance.”

He spoke about what led to the massacre of Aborigines and the attacks on Chinese migrants during the gold rush.

“Unfortunately our nation has dark chapters in our history where racism and ignorance have combined to create tragic results,” he said.

“As policymakers and leaders of this nation it is our responsibility to ensure that racism and ignorance do not combine again. That starts by identifying it and rejecting it.”

Government minister Michaelia Cash drew fire for giving Senator Hanson a warm embrace after her speech and Queensland backbencher George Christensen leapt to Senator Hanson’s defence.

Mr Christensen has since revealed he personally asked Senator Hanson not to run a candidate against him at July’s election.

“But, obviously, they were not looking at ousting an MP who was advocating the same sort of views espoused by One Nation,” he told The Australian newspaper at the weekend. “The views of One Nation to a degree are the views of many in the rank and file of the (Liberal National Party).”

Prime Minister Malcolm Turnbull issued his strongest statement against Senator Hanson’s speech on Friday, saying “tagging all Muslims with the crimes of a few is fundamentally wrong and counterproductive”.

“Seeking to demonise or denigrate all Muslims or seeking to alienate all Muslims and suggest they are somehow not part of Australia or shouldn’t be in Australia, that is exactly what the extremists are saying to the community,” he said.

Mr Alexander holds the seat of Bennelong, held for decades by former prime minister John Howard. Mr Howard says Senator Hanson must be respected rather than demonised or marginalised.

Senator Hanson’s chief of staff James Ashby said on Friday One Nation had hired a former economic advisor to US presidential candidate Donald Trump – but would not name him or give any further details.

“We have just taken him from the Trump camp, so he’s come on board with us, so that’s pretty exciting and we need to build credibility on the economics front,” Mr Ashby told a public forum in Rockhampton.