Thousands of protesters gathered in front of Ontario's legislature Saturday afternoon to rally against proposed service and job cuts in Premier Dalton McGuinty's latest budget.

Members of 12 unions and about 86 community organizations waved signs and flags, shouting "Shame" as various speakers condemned what they called an "unfair" budget.

"In this budget, we saw a lot of things that we certainly didn't like," NDP Leader Andrea Horwath told the crowd at Queen's Park.

"This budget left workers behind."

The demonstration comes three days before the Liberal budget will be put to the test in a crucial vote that may send Ontarians back to the polls.

As the cash-strapped government grapples with a $15.2-billion deficit, the minority Liberals are threatening to legislate public wage freezes, prompting backlash from various groups, including teachers' federations and doctors' associations.

The Progressive Conservatives have already said they will vote against the budget, while Horwath hasn't said whether her recent negotiations with McGuinty were enough to secure her support.

She did, however, say that she would prefer to avoid triggering another election.

Sid Ryan, president of the Ontario Federation of Labour, said it is "shameful" that the burden of paying down Ontario's deficit will be shouldered by ordinary citizens – many of them getting by on mid-to-low incomes or social assistance.

He said the Ontario government should instead introduce a slight increase in corporate taxes, following a similar strategy in British Columbia, which could then be reinvested in health care and education programs.

"Where are we going with this tax-crazed madness? Where is it going to end?" he shouted on stage in front of cheering demonstrators. "What a shameful construct."

Earlier Saturday, Ryan told CTV News Channel that corporations have contributed to the deficit through business-friendly measures such as tax breaks, but aren't being asked to pay down the shortfall.

The rally at Queen's Park was followed by a march through the downtown core. Toronto Mayor Rob Ford did not attend.

Ryan said he hopes the rally will convince McGuinty to "think twice" about his budget and a potential election.

"When he looks out the window at Queen's Park today, a lot of those folks -- school teachers and other people -- have actually worked really hard to elect this government," he said.

The Liberals and the NDP have been discussing a potential deal to avoid sending Ontarians to the polls again.

McGuinty has agreed to deliver on two NDP demands, saying he'll increase support for child care and the Ontario Disability Support Program.

However, the government won't raise taxes to pay for the added social assistance, which means the funds will have to be diverted from other programs.

With files from The Canadian Press