The Ontario government will recall the legislature on Monday after workers at Ontario's power union filed a notice to strike on Friday. The government says it will meet to pass back-to-work legislation to keep power workers on the job and prevent widespread outages.

Friday evening, the Power Workers' Union (PWU) filed a notice to strike to the Ontario Power Generation (OPG), after rejecting its final contract offer. The notice gives 21 days until services are withdrawn.

"We want to assure all people of Ontario, families and businesses, that we're going to take swift action to resolve this matter," said Energy Minister Greg Rickford in a press briefing on Friday.

OPG said in a statement Thursday it "is disappointed that its fair and reasonable offer was not ratified by PWU members."

It would take three weeks to fully wind down nuclear plants in the province, but Rickford said the province could begin experiencing power outages in seven to 10 days.

Rickford said the OPG produces about half of the electricity in Ontario. He said an outage "would be a devastating consequence, not just to the economy but to the safety of families and businesses, so we intend to take whatever steps we need to to ensure that the supply is uninterrupted."

On Wednesday, members of the Power Workers’ Union (PWU) rejected the final contract offer from Ontario Power Generation, which puts workers in a legal strike position. (J.P. Moczulski/Reuters)

OPG CEO Jeff Lyash said the company's goal has been to negotiate a "fair and reasonable" agreement and it's willing to go to arbitration to secure an agreement with the union.

Lyash said the three-year offer rejected by the power workers included wage increases totalling 6.6 per cent, improvement to overtime and shift differentials, and no involuntary layoffs over the term of the collective agreement.

"OPG cares about the safety and working conditions of all of its employees and will continue to move forward in a thoughtful and respectful manner that also ensures the safety of all Ontarians while recognizing the fiscal realities of the company and the province of Ontario," Lyash said in a statement.

'Detailed contingency plans'

The Power Workers' Union represents over 16,000 workers in Ontario's energy sector, including about 6,000 OPG employees.

The union said previously that, "PWU members will continue to fulfil their responsibilities in compliance with all safety guidelines in preparation for job action."

In the statement on Thursday, the OPG said it has "very detailed contingency plans in place and is activating them immediately."

The organization that manages Ontario's power system said Friday that a strike at OPG would put the system's reliability at risk.

"The shutdown of OPG's nuclear and hydroelectric facilities could occur in approximately three weeks. At that point Ontario would not have the generation needed to meet consumer demand and customers would begin losing power," the Independent Electricity System Operator said in a statement.

"The IESO will take every action available to delay and mitigate the impact. Planned generator outages will be deferred, operating reserves will be utilized, and there will be increased use of the gas fleet and energy imports from our neighbours," it said.

"However, these actions will not be enough to prevent significant losses of power."

The union, which has been without a deal since March 31, said in a statement Friday that OPG's final offer was rejected by a nearly 60 per cent vote of its membership.

The main sticking point in talks is OPG's refusal to grant over 300 so-called "term" workers the same rights as full-time employees at the Darlington and Pickering Nuclear Plants, the union said.

"OPG has failed to treat over 300 of its highly trained workforce fairly or responsibly," Power Workers' Union President Mel Hyatt said in the statement. "These employees, like all PWU members, are the backbone of Ontario's reliable electricity sector and should not be treated as second-class employees."