TORONTO - A formal apology to aboriginal people for physical and sexual abuse they suffered at Canada's network of federally-financed, church-run residential schools will help build a better relationship with the country's First Nations, Ontario Premier Dalton McGuinty said Wednesday.

"This painful period in our history must be acknowledged,'' McGuinty told the Ontario legislature. "The prime minister and I are on different sides of many issues, but on this one I am squarely in his camp, because I think it's the Canadian camp.''

McGuinty called the "extraordinary'' apology, to be delivered later Wednesday in the House of Commons by Prime Minister Stephen Harper, an important step because all Canadians bear some responsibility for the residential schools scandal.

"This is part of our history and this is an important way for us to make some of that right,'' he said."It's part of a rebuilding process, part of making progress. I don't think we can really claim to have moved on and found a way beyond that unless an apology is offered.''

McGuinty said the apology will help the province improve its often-strained relations with its First Nations, and help the country to put the residential schools scandal in the past.

"We've been working here in Ontario to lay down a foundation for a stronger, better working and more progressive relationship with our aboriginal peoples,'' he said.

"I think an important part of that foundation will be laid by the prime minister today when he makes a formal apology on behalf of all Canadians.''

The New Democrats tried to push McGuinty to apologize to Ontario aboriginal leaders for conflicts with mining companies that have led to some chiefs being jailed for trying to block exploration on their lands.

"It seems to me, given the recent history of Ontario, this premier has something to apologize for,'' NDP Leader Howard Hampton told the legislature.

"Innocent First Nations leaders were jailed in Ontario under the McGuinty government because they stood up for their treaty constitutional and their aboriginal rights.''

McGuinty didn't offer any apologies, and insisted his Liberal government has taken steps to improve relations with First Nations, including setting up a standalone Ministry of Aboriginal Affairs.

But the Progressive Conservatives said McGuinty has a lot to answer for, especially when it comes to the aboriginal occupation of a former housing development in Caledonia, Ont., which has been dragging on for more than two years.

"We've been looking at Caledonia now for 28 months and we don't see any sign of a solution,'' complained Conservative critic Peter Shurman. "And we see two laws in effect when Ontarians deserve one law for all.''

The federal government conceded 10 years ago that sexual and physical abuse at the church-run residential schools was rampant, but no prime minister has ever apologized.