Malcolm Turnbull and Bill Shorten have "respectfully declined" an invitation to attend next week's historic Indigenous constitution convention at Uluru, wary that their presence could reduce the prospects of a successful outcome.

The Prime Minister and Opposition Leader were invited to the closing ceremony of the four-day convention a fortnight ago, but told the Referendum Council on Wednesday they would not be coming.

Mr Turnbull and Mr Shorten discussed their attendance last week and decided it risked being interpreted as an attempt to influence the outcome. 

"This is the first time an Indigenous designed and led constitution convention has been run and both leaders are very conscious about respecting that process," a spokesperson for Mr Turnbull said.

"The focus of next Friday should be on the hard work done so far," Mr Shorten told Fairfax Media. "The day belongs to the communities right across the nation who have given us the benefit of their wisdom.

"The next step is taking the vision presented in the heart of our nation to the home of our democracy. The Prime Minister and I are united in our determination to achieve constitutional recognition for the first Australians."

The decision is likely to be welcomed by delegates concerned at the prospect of presenting the outcome of the convention to a Prime Minister who will find it difficult to endorse.

This was the result in December 2000 when the Council for Aboriginal Reconciliation presented its final report to then prime minister John Howard.

It means the closing ceremony will present the convention's recommendation to the Australian people, not their political leaders, though it will ultimately be delivered to Mr Turnbull and Mr Shorten by the Referendum Council, co-chaired by Pat Anderson and Mark Leibler.

The convention follows 12 regional dialogues that have rejected the idea of purely symbolic recognition and favoured "substantive" change in the form of an Indigenous voice to the national Parliament or a constitutional prohibition on racial discrimination.

More than 300 delegates will attend the convention against the backdrop of the three big milestones in Indigenous history: 50 years since the 1967 referendum, 25 years since the High Court's Mabo decision and 20 years since the Bringing Them Home report on the forced removal of Aboriginal children.

Both leaders will address Parliament on the significance of the anniversaries on Wednesday, take part in the Long Walk to the MCG, and address a lunch before the Indigenous Round game between Essendon and Richmond on May 27, the anniversary of the referendum.