Pauline Hanson says she has sacked the convicted rapist who worked as One Nation’s campaign manager, but accused Coalition MPs of playing “gutter politics” by criticising her decision to rehire him.

Sean Black, who in 2018 was jailed for rape and subsequently lost his appeal against the conviction, was initially rehired by One Nation in 2020 as a campaign director after serving his time. He remained employed by the party until Sunday, Hanson said.

In a late-night appearance on Sky News, Hanson said “he’s gone, he’s finished” when asked about Black’s employment, and she was “sickened” by criticism from opposition politicians in recent days.

Hanson said she had received “no concerns raised by the other female staff” about Black and that he had “done a great job” since returning to the party following his time in jail.

“It’s gutter politics … and it sickens me to what has happened,” Hanson said.

“[Black] did his time for the crime he was convicted of and that, and now he was trying to get on with his life… What now? What happens? [Put him] on the scrapheap? Or should we bring in the death penalty for anyone who commits a crime?”

Hanson would not be drawn on whether a convicted sex offender, like Black, would appear on One Nation’s proposed public sex offender register but said that policy proposal was mostly intended for paedophiles, and that people who have served time was “another matter”.

“Society has realised that if you do your time, you give back to society. And there’s … not been any offence committed from this man ever since. When are we actually going to stop hounding them and give them their life back? He’s paid his his dues to society,” she said.

The Liberal senator James Paterson had earlier criticised the “absolutely extraordinary” decision by Hanson’s political party to keep a convicted rapist on staff, saying it’s “very hard to take One Nation seriously”.

“It means it’s very hard to take One Nation seriously when they talk about law and order, when they talk about being tough on crime, when they talk about domestic violence,” he told Sky News.

“They have a pretence of being a serious political party, and they are employing a convicted rapist to work for them. I don’t think he should be allowed in Parliament House in sitting weeks, and if he is being brought to Parliament House, they should explain why they think that’s appropriate.”

The Liberal National MP Garth Hamilton had also written to the House of Representatives speaker last week to share his concern about whether Black had been in the building, according to the Courier Mail.

“I want to know when there’s a rapist in parliament,” Hamilton wrote.

Guardian Australia has contacted One Nation for a response.

One Nation’s rise since the 2025 federal election could supplant support for the Coalition as the defacto opposition party in a number of regions, opinion polls suggest.

The upcoming byelection in Farrer will be a test of whether the rightwing party can capitalise on waning support for the major parties, particularly the Coalition.

Paterson said the Liberals would scrutinise One Nation by pointing to its failures, including the number of people it has had elected to parliaments that subsequently quit the party before the end of their first term.

“I mean, this is an extraordinary track record of failure by One Nation, and it really calls into question whether or not they could ever govern in the national interest for all Australians,” Paterson said.

The treasurer, Jim Chalmers, used a speech at a pub event in his electorate on Sunday to warn that Labor’s opponents are a “three-ring circus of rightwing parties” that “desperately want Australia to fail”.

“They’ve made the political calculation that the worse Australians fare, the worse Australia performs, the more divided our politics and societies, the greater dividend for them politically,” he said.

“Take One Nation. At every turn and in almost every vote, when they’ve had the choice between voting how communities, like ours, need them to or voting the way Gina Rinehart tells them to, they make the wrong choice.

“Their reason for being is to capitalise on the politics of division. Our reason for being is providing economic security and creating economic opportunity as the best defence against division and polarisation.”