A view of Canberra from Mt Ainslie.

A view of Canberra from Mt Ainslie. Photo: Karleen Minney

The long-running battle over Canberra's indigenous heritage may never be definitively settled, a confidential ACT government briefing says.

The new evidence means that the government's approach to indigenous affairs since self-government, with the Ngunnawal people recognised as the traditional custodians of the land, has been built on shaky foundations.

An anthropological report released under freedom of information says that the struggle between Ngunnawal and Ngarigu for the mantle of the Canberra's "first people" is unlikely to be solved by science with the evidence gathered from the mid-eighteenth century onward just not good enough to make the call. Another group - the Ngambri - that claims custodianship of the land receives only scant mention in Dr Natalie Kwok's report.

In her study, marked "ministerial in confidence", the anthropologist has found evidence that the local indigenous groups were part of a "broad Aboriginal sociocultural bloc" covering a vast area from Bulli in the north and as far south as the modern Victorian border and to the Snowy Mountains in the west.

The report was commissioned as part of a settlement of a legal action between the Ngarigu of the Monaro and the ACT government, with the indigenous group agreeing to drop

legal action in return for new investigations into the region's Aboriginal heritage.

The legal claim on behalf of the Ngarigu people argued that the group has been left out in the cold for decades by the government when acknowledging Aboriginal culture and history and in providing services to the territory's indigenous people.

Dr Kwok's findings, which she describes as tentative because of the time limits imposed on her research, found no evidence to rule out the ideas of earlier scholars that Canberra was built on the site of a linguistic divide.

She found much evidence to support the view that Ngunnawal lands stretched off to the north of the present-day capital while Ngarigu territory was centred on the Monaro tablelands.

But the records kept in the early days of European settlement are just not good enough to determine definitively which groups lived in what areas of the capital region.

''With few exceptions the early observers failed to take any interest in or record their observations about Aboriginal landed associations,'' Dr Kwok wrote.

''The fragmentary information within official records and local reminiscences is insufficient to recapture the original configurations of identity maintained in the area.''

Dr Kwok said she believed that the Canberra area before European settlement would have had highly complex systems of associations with the land found elsewhere in Australia but that those systems broke down early in the colonial historical piece.

''It is clear that the combined effects of massive demographic stress, alienation from country, forced adjustments and necessary engagements with European settlers led to an early breakdown of original relationships to land and landed identity,'' she wrote.

''Only a detailed ethnographic study conducted at the time when classical structures were still in place could adequately give account of the social and territorial organisation originally existing in the ACT region.''

Dr Kwok concluded that the identity of Canberra's ''first people'' was likely to remain uncertain.