TORONTO - The proposed sale of Crown-owned Atomic Energy of Canada to a Montreal-based engineering firm will lead to higher costs for ratepayers in Ontario, critics warned Tuesday.

Greenpeace nuclear expert Shawn-Patrick Stensil said the sale to SNC-Lavalin Group would hit Ontario residents in their wallets because it would likely put an end to subsidies to build reactors in the province.

"If they privatize correctly and end subsidies, we'll start seeing the true cost of nuclear power," said Stensil.

The reported sale comes two years after Ottawa announced plans to spin off AECL's commercial reactor business and sent Ontario's plans to purchase new reactors into limbo.

It also raises questions about whether any new projects will include cost sharing after years of government support and projects going over budget, said NDP energy critic Peter Tabuns.

"We don't know what kind of guarantees will come in the future," said Tabuns.

"It looks like SNC Lavalin is going to be operating on a buyer beware basis: They aren't going to be providing cost overrun guarantees, something that Ontario was looking for."

The deal puts "a huge question mark" on the electricity plans of the governing Liberals and Opposition Progressive Conservatives, said Tabuns, since unlike the NDP, both those parties are deeply committed to nuclear energy.

"I would say that the huge risk that Liberals and Conservatives were willing to run with investing in nuclear has just become even bigger," Tabuns said.

Energy Minister Brad Duguid welcomed news of the sale, however, saying it will provide more certainty to Ontario's nuclear sector.

He dismissed questions about increased costs, saying he expected the federal government to continue to support nuclear projects even after the sale.

"To be fair, the federal government has an obligation to support the energy industry in Ontario as much as it supports the oil and gas energy in the west and as much as it's pledged to support the energy industry in Newfoundland," said Duguid.

"They indicated during the (election) campaign that they would treat all provinces fairly and equally, and we expect them to live up to that."

Progressive Conservative energy critic John Yakabuski said he hoped SNC Lavalin would continue to meet the energy needs of Ontario, and didn't see any impact on costs if SNC-Lavalin takes over.

"I expect that they've done the math and wouldn't have bid on it if they didn't feel they could be competitive out there," Yakabuski said.

Before AECL was put up for sale in 2009, it submitted a bid for Ontario's new nukes, reportedly asking for $26 billion, or the province's entire budget for a nuclear program at the time.

The province put the project on hold hoping for a better deal, and has since complained that it couldn't move ahead with plans to buy new reactors until the sale was finalized.