Protesters have been outside the old parliament building for more than a week and began a traditional smoking ceremony on Thursday.
In a statement, the Aboriginal Tent Embassy said: “The actions of such protesters who carried out a ‘smoking ceremony’ were done without the knowledge, consent or mandate of the embassy council or traditional owners responsible for the regulation of the Aboriginal tent embassy.
“While we support the concept of non-violent direct action, we do not tolerate the destruction of public and private property.”
A spokesman for the ACT police had launched an investigation, adding: “There has been ongoing protest activity in front of the old Parliament House for the last fourteen days.”
Prime Minister Scott Morrison said at a news conference that he was “disgusted and shaken” by the fire.
He added: “I just think it’s appalling and I think it’s shameful and I think the authorities should act quickly and in accordance with the law and people should take the consequences of their actions.
“I am disgusted and shaken by their behavior that would see Australians come and set fire to such a symbol of democracy in this country.”
Deputy Prime Minister Barnaby Joyce said that if the fire was lit deliberately, it would be “an absolute disgrace”.
“This is Parliament, which for so long has supported the freedoms we have as a democracy, and which has made the decisions that formed us as a nation that fought to increase the rights and corrections of our colonial past,” he wrote. Mr. Joyce on Facebook.
“If anyone tries to make a statement, it’s a very bad one that will be received with overwhelming disgust.”
Opposition leader Anthony Albanese said it was a “very historic building”.
“I had the great honor of working for Tom Uren in that building. It is used by school groups, it is used for educational purposes as well as for functions,” he said.
“It’s an important building and I just hope there is only minimal damage.”
Former Nationals leader Michael McCormack said there should be “quick and serious” consequences for those responsible.
“How shameful. A monstrous attack on our democracy, our history, our sovereignty. This modern penchant for tearing down our past serves no purpose,” he said on Twitter.
Resource Secretary Keith Pitt also weighed in on Twitter, commenting: “Whatever your case is, it is not the answer to set the old parliament building on fire and endanger all of them … Hope everyone is safe.”
The building ceased to be used as the seat of Parliament in 1988 and is now home to the Museum of Australian Democracy.