Ontario's minority Liberals are livid – even threatening an election after only eight months – after the opposition parties joined forces in committee to kill key parts of the government's omnibus budget bill.

CBC reporter Mike Crawley reported that the NDP and the Conservatives were voting together on Thursday to kill "significant chunks" of the bill, including provisions that would change environmental laws.

A statement from Premier Dalton McGuinty accused the opposition of joining forces to "gut" the bill.

'People don't want an election at this time. I don't want an election at this time.'—Ontario NDP Leader Andrea Horwath

"It's absolutely imperative that we pass this budget," the statement said. "And if we cannot pass this budget, we will take it to the people in a general election."

In return, the NDP say the minority Liberals are acting as if they have a majority.

After sitting a week longer than planned, the legislature adjourned with an agreement the politicians would return next Wednesday to vote on the Liberal's budget, which the NDP said they would support to avoid defeating the minority government.

But hours later in a legislative committee, the Conservatives and New Democrats started outvoting the Liberals to pass opposition party amendments.

Liberals, NDP trade accusations

McGuinty says the New Democrats "turned their backs" on their agreement to support the budget in exchange for a tax on incomes over $500,000 and other changes the Liberals made earlier.

Finance Minister Dwight Duncan told CBC News the opposition parties want to have it both ways.

"The Tories, for instance, voted against arbitration sections that are virtually lifted out of their platform, and we had a deal with the NDP," he said.

He said the opposition's changes are large enough that the government would not be able to stick to its austerity budget, "which will lead to a credit downgrade, which will lead to increased interest costs, which will lead to cuts in other places."

Duncan said the premier would visit Lt.-Gov. David Onley next Monday or Tuesday to ask for an election if the opposition changes that limit the government's ability to privatize services and agencies were not withdrawn.

Meanwhile, NDP Leader Andrea Horwath said she never said she would "rubberstamp" the budget and that it was McGuinty who is breaking his word.

"I made a commitment to ensure passage of the budget and I will keep my word," she said in a statement. "I also made a commitment to the people of Ontario, and the premier, to make that bill better at the committee stage. Now the premier is threatening an election. I am disappointed: I expect the premier to keep his word.

"People don't want an election at this time. I don't want an election at this time."

'This is no surprise'

NDP house leader Gilles Bisson said the Liberals should not be surprised by the amendments.

"The budget process itself allows us to amend the budget bill," he said. "We have told the Liberals right from the beginning that we were going to do this, so this is no surprise. I think the government has got to realize it's a minority government and at this point they're acting as if they have a majority."

McGuinty, who needs the support of only one opposition member to pass the budget, said he'd be happy to work with any Tory or New Democrat who wants to "put the provincial interests ahead of their party's own interest."

Earlier in the day, the Tories made it clear they will vote against the budget, saying it failed to curb government spending or address what they say is Ontario's jobs crisis.

The political posturing comes after an election in October last year that saw McGuinty's Liberals return for a third term, this time with a minority.

With files from The Canadian Press