Prime Minister Tony Abbott says he is ready to "sweat blood" to achieve constitutional recognition for Indigenous people.

At a fundraising dinner for the RECOGNISE campaign in Sydney on Thursday the PM said he would like the referendum on whether to recognise Indigenous people in the constitution to happen on the 50th anniversary of the 1967 referendum.

"I hope that it might happen on the 50th anniversary of the 1967 referendum, May 27, 2017. That would be a richly symbolic time to complete our constitution," he said.

"But I do not want it to fail because every Australian would be the loser.

"It is more important to get this right than to try to rush it through.

"We will get constitutional recognition and, when it comes, I suspect that it will take the form of a pact, a heartfelt pact between Indigenous people and conservative Australia," he said.

Mr Abbott also announced another $5 million funding for the RECOGNISE campaign.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 3 minutes 38 seconds 3 m 38 s Abbott will 'sweat blood' to recognise first Australians in constitution ( Brendan Trembath ) Download 6.7 MB

"I am prepared to sweat blood on this," he said.

"This is at least as important as any of the other causes that this Government has been prepared to take on.

"I want this to happen, I want this to happen as quickly as it can."

Opposition Leader Bill Shorten also addressed the dinner and put pressure on the Government to release the form of words the referendum question will take.

"If we were crafting our constitution in 2014 we would not accept the omission of the first 400 centuries of our national history from our national definitive document," Mr Shorten said.

"I believe that without a form of words to explain, without that arresting, rallying cry, without a specific change to advocate, it is just not possible to raise awareness beyond the abstract.

"Without a concrete proposal, we cannot turn the national goodwill into meaningful momentum."