Raymond Bachand added the PQ may try to force a tax hike, knowing the Liberals are leaderless and unprepared to face another election.
"If they're going to increase taxes, I'm going to vote against. They've already damaged – severely – the Quebec economy in the first few weeks," he said.
The PQ's Finance Minister Nicolas Marceau said the government would present a fall budget on Nov. 20.
The last time a budget was presented in the fall was in November 2001, when Pauline Marois was finance minister.
She took the step to deal with the economic uncertainty that followed the Sept. 11 terrorist attacks on the United States.
"Waiting until Spring 2013 will only delay the implementation of the actions necessary to put Quebec on the path of a balanced budget for the next year," said the Marceau.
He said it is a necessity, given the $1.6 billion deficit left behind by the Liberal Party.