US President Donald Trump's son has blasted Labor for calling for right-wing activist Raheem Kassam to be blocked from visiting Australia where he is due to speak at a conservative conference.

The former Breitbart editor-in-chief is appearing alongside his former boss Nigel Farage and former prime minister Tony Abbott at the US-backed Conservative Political Action Conference being held in Sydney for the first time next week.

Labor's Home Affairs spokesperson Kristina Keneally on Tuesday called on the government to cancel Mr Kassam's visa, describing him as a "career bigot" who has made anti-Islam, misogynistic and homophobic comments.

We have Big Tech constantly trying to silence conservatives and now one of the major political parties in Australia is trying to silence @RaheemKassam because of his conservative views. The insanity needs to stop! https://t.co/vtPEZcGl47 — Donald Trump Jr. (@DonaldJTrumpJr) July 31, 2019

But Donald Trump Jr accused Labor of "trying to silence" Mr Kassam because of his conservative views.

"We have Big Tech constantly trying to silence conservatives and now one of the major political parties in Australia is trying to silence Raheem Kassam because of his conservative views," he tweeted.

"The insanity needs to stop."

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In one tweet, Mr Kassam said Scottish Party Leader Nicola Sturgen, who had suffered a miscarriage, should have her mouth and legs taped shut so she could not reproduce.

The 32-year-old also described a female politician as a "wrinkly old ginger bird" and suggested a former British minister "was in the special needs class" at school.

READ MORE What you need to know about the conservative politics conference coming to Sydney

Senator Keneally also said Mr Kassam had campaigned for limited migration to control, what he has described as "large-scale Muslim immigration".

The government has condemned Mr Kassam's comments but rejected Labor's call to cancel his visa.

'Talkfest of hate'

Leader of the Government in the Senate Mathias Cormann described some of Mr Kassam's comments as "disgraceful, highly objectionable and completely outrageous".

"These are disgusting comments and I reject them entirely and utterly," he told the Senate on Wednesday.

However, he was comfortable with government MPs speaking at the same event as Mr Kassam.

"I would make the general point that just because you are at an event, you’re not expected to agree with everything that everybody says at that same event.

"We’ve all been at events in our electorates where people have made highly objectionable points.”

The three day event described by Senator Keneally as a "talkfest of hate" is on track to sell out.

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Liberal MPs Amanda Stoker and Craig Kelly will join former Liberal candidates Warren Mundine and Jacinta Price at the event sponsored by Liberty Works, the American Conservative Union and Advance Australia.

Senator Stoker defended her participation and that of other Liberals in the conservative conference.

"If we are doing our job properly as politicians we should be talking to people from all walks of life," she told SBS News on Wednesday.

"Trying to shame into silence anyone who would speak to a person who is wrong on an issue damages our capacity for constructive democracy."