In a Sunday speech in Melbourne to Jewish community leaders, Mr Shorten argued how any watering down of protections under the Racial Discrimination Act would be a giant step backwards.

"It sends a dangerous, insidious signal that this issue isn't as serious as it was before," he told the annual meeting of the Zionist Federation of Australia.

"There is no place for bigotry, no place for racism, no place for hate speech in modern Australia."

The federal government is proposing to change Section 18C of the act, removing provisions that make it unlawful to "offend, insult, humiliate or intimidate" someone because of their race or ethnicity.

Instead, new provisions would make it unlawful to "vilify" or "intimidate" people based on race or ethnicity.

But Mr Shorten said there isn't a better example of how important the current provisions are than the case of Holocaust denier Frederick Toben.

In a landmark decision, the Federal Court had found some pages of his website breached the act - where he accused Jews offended by Holocaust denial of having limited intelligence and that the number of Jews killed in World War II had been exaggerated for financial gain.

He said it was significant that the Executive Council of Australian Jewry has already determined that the 2003 legal win would be unlikely to succeed in 2014 if the act is changed.

"This is proof enough that the government should not be tampering with these protections," Mr Shorten said.

"Doesn't this nation have more important challenges than tampering with these protections?"

Senator George Brandis insisted last week that Holocaust denial will remain unlawful.

"I can't see how Holocaust denial fails to be racial vilification," he said on Wednesdsay.

But some Jewish leaders disagree and a recent poll found most Australians are against weakening the act.

Mr Shorten urged the Jewish community on Sunday to send a message to the Abbott government about the proposed law changes.

"We've got six weeks to change the government's mind on this issue," he said.

"This is a colossal mistake and one with potential disastrous consequences."

After the speech, the Zionist Federation of Australia formally called on the government to scrap the proposed changes.
In a motion passed on Sunday night, the group labels the proposed changes to racial vilification laws as ‘‘deeply flawed’’ and a risk at giving a green light to the incitement of hatred.

The ZLA motion states that current laws provide a proper balance between free speech and racial vilification, so the government needs to reconsider its position.

‘‘It’s a very strong message,’’ said newly-elected ZFA president Danny Lamm.

‘‘And we’ll join with other organisations in conveying to the attorney-general our distress at these changes.’’