A working group on the Indigenous voice referendum is finalising its advice to the government.

The group confirmed legislation setting up the possible constitutional change would be introduced to parliament by the end of the month.

It will contain the wording of the question that is expected to be put to the public between October and November.

"We are close. A decision will be made next week," group member Marcus Stewart told AAP.

"We are committed to ensuring the amendment is as strong as possible, as the Australian public and Aboriginal communities would expect.

"There is no room for mediocrity in this process. We look forward to finalising our advice next week."

Once the bill is introduced it will be referred to a parliamentary committee for an inquiry, which will invite public comment.

The group issued a communique after meeting in Canberra on Thursday.

"The working group noted that this would provide Australians, including First Nations people, with the opportunity to make formal submissions," it said.

The group also held talks with Greens leader Adam Bandt and the party's Indigenous spokeswoman Dorinda Cox.

Liberal frontbencher Simon Birmingham said the opposition was looking for certainty about what the voice would look like.

"I hope we can see a proposal put forward that ensures what Australians are voting on delivers on constitutional recognition but is constitutionally as conservative as possible to give it the greatest chance of success," he said.

"I hope the working group, I hope the government, are pursuing an approach that can give people maximum confidence by having a model that is as careful and conservative in its wording as possible."

Labor is in negotiations with other parties and crossbenchers on how information will be provided to the public and the treatment of donations.

Advocates want to boost Indigenous enrolment rates before the referendum and allow people to register to vote on the day, rather than weeks beforehand.

GetUp chief executive Larissa Baldwin-Roberts said the amendments would undo years of suppression and ensure thousands of Indigenous people could vote.

"We saw how similar reforms in the Northern Territory elections increased voter turnout," she said.

The Greens have called for similar reforms, along with options to allow more remote polling and make voting by phone a possibility, similar to what took place at the last federal election.

The Indigenous enrolment rate was sitting at 84.5 per cent in December, up 2.6 per cent since June.

However, there were still 87,000 voting-age Indigenous people not enrolled.

By comparison, 97.2 per cent of the total Australian population is enrolled to vote.