The Abbott Government is facing a united backlash from its Coalition colleagues in Victoria and New South Wales over proposed changes to racial discrimination laws.

The two most populous states have lodged formal submissions opposing the changes, warning they would weaken protections against racial vilification and threaten social cohesion.

They are urging Federal Attorney-General George Brandis to abandon plans to repeal section 18c of the Racial Discrimination Act.

The change would prohibit vilification and intimidation on the basis of race, but make it lawful to insult, offend or humiliate.

The NSW and Victorian governments released a joint statement arguing "the proposed changes threaten the social cohesion and well-being of not just our states' culturally and religiously diverse communities, but also the wider Australian community".

NSW Premier Mike Baird said the two governments are prepared to defend their multicultural communities.

"The concerns across the multicultural communities in this state are saying 'we're worried, we're afraid', and we're standing up for them," he said.

"We're prepared to stand up for what we think is right."

Victoria's Multicultural Affairs Minister Matthey Guy says the two states are "as one" on the issue.

"There should be no changes to the federal Racial Discrimination Act and we'll be very, very clear in our submission to say so," he said.

"The Victorian Government stands very firmly against any changes to the federal act."

It is a position backed in formal submissions by a range of groups representing multicultural and Indigenous communities.

Submissions to the Government regarding the proposed changes closed on Wednesday, with one warning of race riots seen in Cronulla in 2005.

Kirstie Parker from Close the Gap says racism makes Indigenous people "sick".

"It also further disenfranchises us from society and it underwhelms our sense of personal security and safety," she said.

However, others argue protections against racism are covered by exisiting criminal laws.

"The human right at stake here is one of freedom of speech," said Simon Breheny from the Institute of Public Affairs.

"It's important that the Government repeals section 18c so that freedom of speech can be restored."

A spokesman for the Attorney-General says all submissions will be reviewed and taken into consideration before a draft bill is put to Cabinet in the coming weeks.

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