• Captain Cook’s cottage graffitied with invasion claim

Monarchists have warned of “almost certain violence” if there is a referendum to recognise Aboriginal people in the constitution.

Prime Minister Tony Abbott has described the constitutional change as an “important national crusade”, and has promised to put forward a draft amendment by September.

But the Australian Monarchist League says there is a real prospect of violence by those who are “hostile” to white settlement.

“The appalling desecration of Captain Cook’s cottage in Melbourne by anti-Australia Day vandals will cause many people to resile from the very thought of a referendum and the now almost certain violence that will accompany it,” the group’s national chairman Philip Benwell said.

Police were called to the cottage on Friday after it had been graffitied with the words: “26th Jan Australia’s Shame!!!”.

Mr Benwell says the 2012 Australia Day riot in Canberra, which resulted in then-prime minister Julia Gillard and Mr Abbott having to be rescued from a group of angry protesters, adds to his concern about having a national debate.

“This is a matter of concern to us, that anyone who may express doubts about the proposals may face the sort of vandalism or violence that has accompanied anti-Australia Day protests,” he said,

He says the Australian Monarchist League is not opposed to reconciliation, but it will not support any change that would be “detrimental” to the constitution.

“Certainly the white settlement was not without its problems, but had the British not colonised this country and brought with them the concept of law and order, Australia would not be the great and united nation it is today,” he said.

The former Labor government promised to hold a referendum to recognise Aboriginal people in the constitution, but decided to delay a vote, citing the need to build more public support for the change.