A day before it will deliver a historic official apology to aboriginal people abused or otherwise harmed within Canada's residential school system, the Conservative government came under fire Tuesday for refusing to provide time for aboriginal leaders to respond.

About 250 former students, church officials and other guests have been invited to Parliament Hill to witness Prime Minister Stephen Harper's statement.

All political parties have agreed to cancel the regularly scheduled Question Period at 3 p.m. ET to make time for the apology, which is being delivered on behalf of all Canadians.

Some MPs, however, said the Conservatives should also be making time to allow for aboriginal leaders to respond directly to Harper's apology, expected to run about 15 minutes, in the Commons.

"Surely, this House owes survivors the courtesy of listening to them in return, right here, immediately, on the official Hansard," Manitoba Liberal MP Tina Keeper said during Question Period on Tuesday.

Her request was rebuffed by Harper, who said the parties should not play politics with the matter.

"The government has received a number of suggestions and recommendations on the process for tomorrow," Harper said. "We have looked at all these; we have considered them in the context of our traditions and obviously precedents that have been established in similar solemn occasions."

Keeper said that, in the interest of reconciliation, the House could put aside 30 minutes for a response from those who were at risk of being left "voiceless" in the apology process.

Her sentiments were echoed by Liberal opposition leader Stéphane Dion, who called on Harper's Conservatives to release a copy of the apology text to aboriginal leaders on Tuesday in order to allow them time to prepare a proper response.

At least 30 events have been planned across Canada to give the public a chance to watch the event on television.

Indian Affairs Minister Chuck Strahl has said the apology will be a respectful and sincere recognition of widespread cultural devastation, physical trauma and sexual abuse affecting generations of aboriginal people to this day.

Overseen by the Department of Indian Affairs, the government-funded, church-run residential schools aimed to force aboriginal children to learn English and adopt Christianity and Canadian customs as part of a government policy called "aggressive assimilation."

There were about 130 such schools in Canada, with some in every territory and province except Newfoundland, Prince Edward Island and New Brunswick, from as early as the 19th century to 1996.

In all, about 150,000 First Nations, Inuit and Métis children were removed from their communities and forced to attend the schools, where many of them lived in substandard conditions and endured physical, emotional and sexual abuse.

With files from the Canadian Press