Ontario's largest labour federation says whoever is elected to be the province's new premier in Toronto this weekend will have to face the largest protest of the party's eight years in government.

The OFL says 131 buses travelling "from every corner of the province" are expected to join thousands of protesters at the leadership convention in downtown Toronto.

"The Liberals have tried to pretend that their only opposition is from school teachers, but nothing could be further from the truth. Saturday's rally will be as broad and diverse as the province," Ontario Federation of Labour president Sid Ryan said in a statement Saturday morning. "The Liberals have betrayed their supporters and alienated voters by pursuing an aggressive austerity agenda of deep cuts to jobs and social programs that are vital to every community.

"They have shuttered our legislature and shelved our democratic rights. They have put the province in turmoil."

"This rally won't simply be education workers and labour unions, it will draw thousands of students, parents, seniors, environmentalists, Aboriginal people, anti-poverty activists and everyone in between," said Ryan. "The new premier will see the many faces of their opposition - from now and into the next election."