OTTAWA (AP) — Canada's aboriginal affairs minister has resigned after improperly advocating to a tax court on behalf of a constituent he represents in Parliament.

Prime Minister Stephen Harper announced John Duncan's departure Friday afternoon. Duncan released a statement soon afterward explaining his decision. Duncan will keep his Parliamentary seat representing a Vancouver Island district.

In recent months, Duncan faced nationwide protests by the aboriginal community over treaty rights. He has suffered from poor health and was considered one of the government's less effective officials.

The position of aboriginal affairs minister is likely to take on a much higher profile in during a new round of negotiations over treaty issues and land-claims settlements to which Harper has committed. Heritage Minister James Moore is temporarily taking over the post.