Opposition Leader Tony Abbott has confirmed he will propose an amendment to recognise indigenous Australians in the constitution if the coalition wins September's election.

Mr Abbott has adopted the words of former Labor prime minister Paul Keating saying the state of indigenous Australians constitutes a "stain on our soul".

"I think that recognising indigenous people in the constitution is an idea whose time has come and I certainly want to take that forward if the coalition does win the election," he told ABC radio.

"We shouldn't be on about striking poses. We should be on about doing what is genuinely in the national interest, and it's genuinely in our national interest that we do achieve lasting and complete reconciliation with indigenous Australians.

"As Paul Keating said back at Redfern all those years ago, the state of indigenous Australia does constitute a stain on our soul and we do have to get it right one day, and we certainly have to do it better in the future than we have done it in the past."

Mr Abbott said the proposal was not about looking good, but doing good.

He will deliver a speech on reconciliation at the Sydney Institute on Friday night.