TORONTO - Author Margaret Atwood, actor Cathy Jones and musician Sarah Harmer are among 20 prominent Canadians calling on Premier Dalton McGuinty to immediately free seven jailed aboriginal leaders and stop controversial mineral exploration across the province.

In a letter being sent to McGuinty on Tuesday, the group -- which also includes former UN ambassador Stephen Lewis -- pleads the case of jailed aboriginals trying to stop mining in their traditional northern territory, and says mining shouldn't take precedence over people's homes and health.

Six members of the Kitchenuhmaykoosib Inninuwug (KI) First Nation, including Chief Donny Morris and Deputy Chief Jack MacKay, were sentenced to six months in jail last December after ignoring an injunction allowing Platinex to start drilling on traditional aboriginal territory 600 kilometres north of Thunder Bay, Ont.

Retired Algonquin chief Bob Lovelace was also sentenced to six months in jail for his role in opposing a uranium project in eastern Ontario.

"We support the right of a community to say NO to mineral exploration and mining projects that threaten the health of people and ecosystems in Ontario,'' states the letter, which also notes a grandmother will spend her 60th birthday behind bars for protesting mineral exploration on her traditional land.

"These are fathers, mothers, sons, daughters, grandfathers and grandmothers.''

McGuinty must immediately free the jailed leaders and stop mineral exploration both in northern and eastern Ontario, the letter states.

The governing Liberals also need to overhaul the 100-year-old mining act to ensure this doesn't happen again, the group added.

Ontario's current "free entry'' system allows companies to come into people's backyards to look for minerals without permission with little recourse for anyone who wants to stop it, they said.

Instead, the group said mining companies should only be granted exploration permits after proper environmental assessments and real consultation with aboriginal communities.

This will ensure "the health of the people of Ontario and its vital ecosystems will be protected,'' said the letter, obtained by The Canadian Press.

Angus McKay, one of the few remaining councillors left at the KI band office, said the group is grateful for all the support it has received across the country. There is more at stake than the freedom of the six jailed leaders, he said.

"This issue touches every native band,'' McKay said. "It's far-reaching. It's not just about mining. It's not just about Platinex. It's also about human rights.''

Aboriginal Affairs Minister Michael Bryant has said the government has offered $200,000 toward the legal fees of the jailed aboriginal leaders and is willing to do more if they decide to appeal their convictions.

But both McGuinty and Bryant have said they can't interfere with the court process or unilaterally release the jailed leaders.