Ontario Education Minister Laurel Broten announced that she will impose new contracts on teachers, a move that threatens to intensify labour unrest in the province's schools.

Citing the stubborn $14-billion deficit, Ms. Broten said Thursday that she had a choice between protecting gains in the public education system and raising teachers' salaries.

In imposing the two-year contracts banning teachers from walking off the job, Ms. Broten said: "I have been left with no other option."

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"In the end, action was necessary and we have taken it," she said at a news conference.

However, Ms. Broten stressed that the controversial legislation known as Bill 115 is a one-time measure. The plan, she said, is to repeal the legislation well before the two-year contracts expire on Aug. 31, 2014.

Ms. Broten warned union leaders not to ask their members to take "illegal strike activity," saying teachers are no longer in a position to walk off the job.

Sam Hammond, head of the Elementary Teachers' Federation of Ontario, warned that "you cannot expect that it will be business as usual in schools" when classes resume on Monday.

However, he did not offer any specifics beyond a previously announced court challenge to the legislation, saying union leaders needed to meet first.

Mr. Hammond described the government's use of Bill 115 as a "disgraceful use of government power."

"A decade of goodwill has been squandered in just under 10 months by this education minister," he said at a news conference, where he accused Ms. Broten of "trampling" teachers' bargaining rights.

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The government will not "remove the stain" of Bill 115 of simply repealing it once it has been used, he said.

The deadline for unions to reach local agreements with school boards came and went on Monday night, giving Ms. Broten the power to set the terms of the contracts for public school teachers and staff under Bill 115, which allows the government to freeze wages, reduces teachers' ability to bank sick days and limit their right to strike.

Only 65 of 469 school bargaining units across the province have come to deals that meet the province's strict requirements under Bill 115, the vast majority of them within the English Catholic school board, which settled in July.

Elementary teachers staged rotating one-day strikes across the province before the Christmas break and in late December ETFO urged Ms. Broten to hold off on imposing contracts until a new Liberal leader is chosen to replace Mr. McGuinty.

But it is unclear whether ETFO plans to escalate strike action, which could be deemed illegal. High school teachers across the province have withdrawn from extracurricular activities, which they provide on a volunteer basis. That job action is expected to continue into 2013 – and for the next two years – because of the province's move to impose contracts.

Opposition members denounced the government for announcing that it plans to repeal the legislation after using it to impose a new contract.

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"What we've just witnessed is cynical politics at its very worst," New Democratic MPP Cheri DiNovo told reporters.

Progressive Conservative Leader Tim Hudak, who has been pushing for mandatory, across-the-board wage freezes for public sector workers, criticized the government for planning to repeal its legislation that imposes such a freeze on the province's teachers.

"It's been 10 months of this chaos," Mr. Hudak told reporters on Thursday. "Now they're going to toss it overboard? That tells me they want to put the union bosses back in charge of this process."

Annie Kidder, executive director of the advocacy group People for Education, said she doubts that repealing the legislation will solve the problem or restore a sense of "collegiality" between the government and teachers.

"It's like giving with one hand and taking away with the other," Ms. Kidder told reporters.

The Ontario Liberals have said that cutting teachers' paid sick days to 10 from 20, and delaying a pay grid that increases their salaries to $90,000 from about $40,000 over 10 years, was necessary to tackle a $14-billion provincial deficit while preserving job-generating programs such as caps on primary-class sizes and full-day kindergarten.