The so-called counter-summit is being organized by Common Causes, an assembly of groups dedicated to those causes.
Maude Barlow, chairwoman of the Council of Canadians, said she is concerned about the agenda of the Conservative party.
"We think this is an extreme agenda and this government doesn't have the mandate for it," Barlow said in an interview. "We will be there to speak out against these policies and to put forward more progressive policies."
The summit includes an event called Pros & Cons: Policies for People and the Planet. It's billed by Barlow as an opportunity to learn about the potential impacts of proposed Conservative policies.
Participants include a number of prominent Conservative critics: including Barlow, environmentalist David Suzuki and Paul Moist, president of the Canadian Union of Public Employees. Chief Theresa Spence from the Attawapiskat First Nation was scheduled to attend, but cancelled to attend to an emergency at home.
Barlow accuses the Harper government of gutting environmental legislation, giving tax breaks to the energy sector and signing long-term trade deals she considers dangerous. She also accuses the government of lacking accountability, attacking unions and undermining universal health care.
"Canadians should be really concerned both with what's happened and with what they're looking at," she said. "I believe we're looking at an extreme Conservative agenda that's intended to put in place the Harper vision long after Stephen Harper is gone."
The secretary-general of Confederation des syndicats nationaux, one of Quebec's most influential labour unions, said the Conservative government has launched an attack on the 4.3 million people within the labour movement and is infringing on rights that have long been recognized in Canada.
"Never before has the federal government gone so far in an attack on working people," said Jean Lortie.
"There's a frontal assault on their right to organize, the right to negotiate collective bargaining in a proper environment and now the right to legitimately strike or do pressure tactics whenever you want to negotiate an agreement."
Barlow also accuses Harper and the Conservatives of misplacing their "moral compass" and predicts they won't bounce back from the public outrage surrounding the Senate expenses scandal.
"It has compromised his reputation with his base and I think it's done. I think the damage is too great and he won't be able to climb out of it."
The counter-summit was planned for just after Harper's address to the policy convention Friday night.
A protest was also scheduled for Saturday outside the convention.
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