Burn the flag, you're an idiot: Shorten

If you burn the Australian flag, you're an idiot, according to Bill Shorten.

The opposition leader made the comments after protesters burned flags during violent clashes in Melbourne on Sunday.

And Mr Shorten reckons 99.99 per cent of Australians agree with him.

"Anyone who burns the flag is an idiot," he told reporters in Melbourne.

But he doesn't think the nation needs a law to prohibit the fiery act.

"Frankly, I think everyone knows it's a stupid, idiotic thing to do."

Nationals MP George Christensen in February introduced a private bill to parliament to make it criminal to mutilate or destroy the Australian flag.

Critics fear such a law would limit free speech, an issue also raised by parliament's human rights committee.

Police are reviewing CCTV footage in hopes of identifying those responsible for the violence at the weekend's rival anti-racism and anti-immigration rallies in Melbourne.