An opposition MP has resigned from Australia's shadow cabinet to campaign to give indigenous people a voice.

The Liberal Party's Julian Leeser has resigned, after his party confirmed it will oppose the change to the country's constitution.

Australian correspondent Murray Olds says he's supported the cause a long time.

"This is something he's been working on for a decade. He has been campaigning for 10 years, longer maybe, for indigenous Australians, first Australians, First Nations people."

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