Australian Greens leader Adam Bandt said he was sad to see Senator Lidia Thorpe leave the party but offered no further details on the Greens' stance on the Voice on Monday.

"Senator Thorpe leaves the Greens with an enormous amount of respect. She is a fighter for her people," he said.

"She has helped put Treaty, raising the age of criminal responsibility on the parliamentary agenda."

Mr Bandt said if Senator Thorpe had ultimately reached a different position to the party on the Voice, he was prepared to take over as spokesperson on the Voice so she was free to publicly express her own opinions.

"I made it clear to Senator Thorpe that she still had a place in the Greens and that I wish she had continued in the Greens," Mr Bandt said.

"Including as the party's First Nations spokesperson, that she had the right to, of course, under our Constitution, vote differently on the question of Voice and, if she came to a different position on the question of Voice, that I would take over responsibility for being the party spokesperson on Voice so that she would be free to speak her mind."

After making his statement, Mr Bandt was asked about his position on the Voice.

"The Greens want to see progress on all elements of the Statement from the Heart on truth, treaty and voice," he said.

"Last week, we spent a couple of days discussing this very important matter, and we've got further meetings scheduled, including one this evening, while parliament is sitting.

"We still have our processes to work through. But we're taking it seriously and we're talking about it while parliament's sitting."

Senator Thorpe's resignation and moving to the cross bench impacts the balance of power in the Senate.

Labor holds 26 of the 76 seats in the Senate and needed the support of the Greens 12 seats, plus one independent to reach a majority and pass legislation.

The Labor government now needs the Greens, plus two other Senators to pass anything in the Senate.