At least 6,000 aboriginal children died while in the residential school system in Canada, in a "cultural genocide", officials have said.

Justice Murray Sinclair, Chair of the Truth and Reconciliation Commission, who is responsible for studying the legacy of the residential schools, said the figure is an estimate and the true figure could be much higher.

"We think that we have not uncovered anywhere near what the total would be because the record keeping around that question was very poor," Sinclair told Rosemary Barton of CBC's Power & Politics. "You would have thought they would have concentrated more on keeping track."

The new death toll comes after comments from the chief justice of the Supreme Court, Beverley McLachlin, who said that Canada attempted to commit "cultural genocide" against aboriginal peoples.

"The most glaring blemish on the Canadian historic record relates to our treatment of the First Nations that lived here at the time of colonization," McLachlin said.

Canada, she said, sustained an "ethos of exclusion and cultural annihilation", an assessment which Justice Sinclair agreed with.

"I think as commissioners we have concluded that cultural genocide is probably the best description of what went on here.