Ontario's Liberal government spent $468-million to buy labour peace with the province's teacher unions, giving some educators pay hikes and others richer benefits.

The revelation, by Auditor-General Bonnie Lysyk Wednesday, runs counter to the Liberals' long-held narrative – that they persuaded the unions to end a politically damaging work-to-rule campaign last year with little more than a promise to create a new negotiating framework for future contracts.

Getting the unions back on side was a major victory for Premier Kathleen Wynne, whose party has long relied on teachers as election-time volunteers and a key part of their winning coalition.

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In 2012, the province imposed austere contracts on public-school teachers through legislation, freezing their pay and partly eliminating a sick-day bank in a bid to save money. The measures caused major blowback for the government. Teachers stopped running extracurricular activities and helped the NDP defeat the Liberals in a crucial by-election.

The government then made a series of concessions, including a raise for elementary school teachers that cost the treasury $113-million, plus $155-million worth of various benefits such as longer maternity leaves and fewer unpaid professional days. Earlier deals with separate school teachers and support staff, meanwhile, increased the number of sick days, which triggered me-too clauses across the education sector and cost $200-million.

Taken together, the expense to taxpayers adds up to $468-million, Ms. Lysyk told a Queen's Park news conference, shaving a big chunk off the savings the Liberals had achieved with the legislated contracts.

"That is the total for the additional cost," Ms. Lysyk said. "The savings were reduced."

She found that the government's revised $2.1-billion estimate of the savings to the treasury was "reasonable," but that the savings would have been higher without the concessions.

Education Minister Liz Sandals refused to answer questions about the cost of the concessions, before fleeing down a hallway and into the cabinet room, pursued by reporters and television cameras.

"I think that's a very odd question," she said.

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Lori Foote, a spokeswoman for the Ontario Secondary School Teachers' Federation, said the union will not comment until it has a chance to review Ms. Lysyk's report. The Elementary Teachers' Federation of Ontario did not respond to a request for comment.

The government has previously made public some of the costs of the various agreements with teachers and support staff. Others, however, were kept quiet.

When OSSTF and ETFO ended their work-to-rule campaigns, Ms. Wynne and Ms. Sandals portrayed the victory as the result of a simple government pledge to revamp the way future deals would be bargained. Ms. Sandals also said some enhanced benefits for teachers would be cancelled out by savings from the earlier legislated contracts.

In press releases issued after the deals with separate school teachers and the Canadian Union of Public Employees, which represents support staff, the government trumpeted the money it would save but not the costs of the enriched benefits it had agreed to.

The opposition parties said the Liberals had not been up-front that the unions had agreed to get back to voluntary activities because of concessions, or that those concessions had slashed the government's savings.

"The government wasn't honest, it wasn't truthful and it wasn't transparent," Progressive Conservative MPP Lisa MacLeod said. "It's clear that the Liberals didn't want to tell the whole truth, particularly before the election."

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New Democratic education critic Peter Tabuns said the province could easily have tallied up the cost of the various deals, as Ms. Lysyk did, and released it.

"You asked questions that the government could answer with some very straightforward calculations," he told reporters. "This is not a government that has been particularly transparent on these matters. You tried to get answers, they stonewalled you."

With a report from Caroline Alphonso