Secretary of the Prime Minister and Cabinet Department Ian Watt, will chair a meeting in Canberra next month of nine of Australia's most powerful public servants to discuss the service's dismal recent record on hiring and keeping indigenous staff.

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The Canberra Times revealed on Saturday Mr Watt's department had drafted in 260 Aboriginal bureaucrats and 860 of their non-indigenous colleagues from the old indigenous affairs department to help ''close the gap'' and left them the losers in a two-tier pay system.

The move transformed PM&C at a stroke from the public service's whitest department to one of its most culturally diverse, but the new recruits from the Department of Families, Community Services and Indigenous Affairs have been kept on wages up to $19,000 below those paid to their new PM&C colleagues.

Mr Watt has not responded to a request for an interview about wages equality in his department and it is unclear if he will raise the topic with the other nine members of the ''Diversity Council'' when they gather in southern Canberra on March 9.

The meeting was originally scheduled for Wednesday.

The council, which includes the bosses of the three largest departments, Human Services, Tax and Defence as well as the chiefs of other key agencies, was formed in 2012 to try to boost government hiring of Aboriginal and Torres Strait Islanders.

But indigenous public servants are quitting their jobs at 1½ times the rate of their non-indigenous colleagues, the latest data shows, and the bureaucracy's bosses still do not know why.

The proportion of Aboriginal and Torres Strait Islander employees has been in steady decline in the service since 2002 and is now below the government's target of 2.7 per cent.

Indigenous employment in the service was 2.3 per cent, or 3846 workers, in June, down from a high of 2.8 per cent in 2002.

Research is under way to try to understand the higher churn rate among indigenous workers.