Indigenous senator Lidia Thorpe has justified her roundly criticised protest action against King Charles, saying she had written to the monarch multiple times and he ignored her.

The independent from Victoria confronted the King and Queen Camilla during a welcome reception at Parliament House on Monday, before being kicked out.

“You are not our king. You are not sovereign,” she shouted.

“You committed genocide against our people. Give us our land back. Give us what you stole from us – our bones, our skulls, our babies, our people.

“You destroyed our land. Give us a treaty. We want treaty.”

Speaking on Tuesday, Senator Thorpe said her repeated written requests for a meeting and a “respectful conversation” with the monarch had been ignored every time.

“That wasn’t afforded to me, so I did that for my people. I did that for my grandmother, and I wanted the world to know that we need a treaty here and we want an end to this ongoing war against first peoples in this country,” she told ABC radio.

“I don’t subscribe to assimilating myself into the colonial structure.”

Senator Thorpe doubled down on her accusation the King was complicit in the genocide of indigenous people by remaining silent.

“Why doesn’t he say, I am sorry for the many, many thousands of massacres that happened in this country and that my ancestors and my kingdom are responsible for that,” she said.

Asked about her affirmation of allegiance to the crown when she was sworn in as a parliamentarian, Senator Thorpe said she did that under duress and to fulfil her duties.

Senator Thorpe demanded the UK hand back indigenous artefacts and remains that had been taken.

King Charles spoke quietly with Prime Minister Anthony Albanese while they sat on a podium in the Great Hall, as security officers stopped Senator Thorpe from approaching further and escorted her from the room.

Senator Thorpe, who was a guest at the event, was criticised by other guests at the reception including former Liberal prime minister Tony Abbott and Victoria Cross recipient Keith Payne.

Opposition Leader Peter Dutton labelled the senator’s protest an act of “self-promotion” and said she should consider resigning.

“People need to express themselves respectfully and sometimes people make it all about themselves and I think that’s what yesterday was,” he told the ABC.

Labor minister Amanda Rishworth said Senator Thorpe’s actions were “pretty disrespectful and not just to the King, but to the many great Australians that had gathered in the Great Hall”.

NSW Premier Chris Minns, who will on Tuesday host a community barbecue for the royal couple, said Senator Thorpe’s protest was “grossly disrespectful”.

“Everything that particular senator does seems to revolve around herself, as if she’s attempting to make herself, that senator, the focus of all attention,” he told Sydney’s 2GB radio.

The coalition is considering raising a censure motion against Senator Thorpe in the upper house when it next sits in November.

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