A day that should have been a celebration of national unity was marred by ugly scenes as violence broke out at a Sydney ‘Invasion Day’ protest, leaving a police officer injured.

And while dissenting groups played out their frustrations and differing opinions on the street, senior Liberal politicians were just as vocal Thursday in their opposing opinions on the future of Australia Day.

At least one police officer was injured and an Australian flag was burned as wild scenes emerged from an Invasion Day march from Redfern to the Sydney CBD.

Police used an extinguisher to put out the burning flag and an officer sustained injuries during the ensuing scuffle, police said.

NSW’s new Premier Gladys Berejiklian condemned the violence.

“We have a democracy and everyone has a right to protest, but today is celebrating everything that brings us together, and I think most people would feel extremely disappointed at what they have seen today,” she said.

“It’s not acceptable to do that on a day like today, however please feel free to express your views.”

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Video of the incident shows pushing between police and protesters, with several people knocked to the ground, and white smoke can be seen coming out of part of the crowd.

Police said that although burning an Australian flag was not an offence, they were concerned about the potential consequences of the fire.

One man was arrested during the Sydney Invasion Day march. Photo: Twitter/Allan Clarke

A 20-year-old man was arrested and the injured police officer was taken to hospital.

Invasion Day protests also took place in other major capital cities, and outside Parliament House, where hundreds gathered to call for an Aboriginal treaty.

About 10,000 people gathered in the centre of Melbourne, bringing the CBD near Federation Square to a standstill, while city roads were also blocked for a protest in Brisbane.

About 10,000 protesters gathered at Melbourne’s Invasion Day protest. Photo: AAP

Date debate

Meanwhile, a split emerged between Liberal Party figures weighing in on the growing controversy around the January 26 date.

Prime Minister Malcolm Turnbull said people were entitled to debate the issue, but confirmed the government’s support for the existing day.

The Deputy PM says debate around Australia Day is political correctness. Photo: AAP

“There are many bigger, more profound issues like constitutional recognition [for indigenous Australians] to deal with than the date of Australia Day,” Mr Turnbull said.

Deputy Prime Minister Barnaby Joyce went further, suggesting the call to change the date was political correctness gone mad from people who were “miserable”.

“Today is a day about celebration,” Mr Joyce told Sydney’s 2GB radio on Thursday.

“I’m just sick of these people who every time they want to make us feel guilty about it. They don’t like Christmas, they don’t like Australia Day, they’re just miserable … and I wish they’d crawl under a rock and hide for a little bit.”

Call for change

Malcolm Turnbull says there’s no need to change the Australia Day date. Photo: Getty

The comments came after former Coalition cabinet minister Ian Macfarlane wrote an opinion piece for The Australian newspaper that called for the date to be changed.

“Why do I think we should we change the date from January 26? Simple. Because not all of us feel the same way about that date,” he said at an Australia Day breakfast in Melbourne.

“It was the moment I decided that as a conservative, Anglo-Celtic Australian, I want to play a part in the push to changing the date of Australia Day.

“It’s about healing a wound, drawing a line, getting on with the really important issues facing our indigenous communities.”

Responding to a defence of the date from Treasurer Scott Morrison, Mr Macfarlane added: “Scott’s not right. It isn’t a day where all Australians can celebrate. It is a day that some indigenous people find very hurtful.”