The opposition leader also rapped the Tories for conducting months of secret talks about joining the organization and coming clean about the offer only days before a final decision is to be made.
"We are strongly against (it)," Dion told the Star.
The initiative proposes that nuclear energy-using countries and uranium-exporting countries band together to promote and safeguard the industry. Under the proposal, all used nuclear fuel would be returned to the original uranium-exporting country for disposal.
Foreign Affairs Minister Maxime Bernier told reporters in Sydney, Australia, yesterday that, as a major uranium producer, Canada has "considerable interests" in how the world decides to proceed with development and distribution.
"So we will have a decision in the near future about our participation," Bernier said.
Canada is the world's top producer of uranium, responsible for about one-third of the world's supply.
Ottawa already has a report by the Nuclear Waste Management Organization proposing several ways to manage nuclear waste, but it has not been made public.
Dion called for the Tories to make it public and to hold a public debate in Parliament before deciding whether to sign on to the nuclear partnership.