Quebec's Auditor General says the government's finances are in much worse shape than previously thought.

Coming the day before the Liberals unveil their first budget the auditor general says the Parti Quebecois estimate of provincial finances was off by $4 billion.

"In the budget the gap is $150 million but what we have seen with our work it's $4 billion," said Michel Samson.

That means Quebec's deficit is not around $1.75 billion, but is actually $5.6 billion.

Auditor General Michel Samson agrees the financial situation is dire and urgent action is needed.

He said the PQ should have made deeper cuts and should not have promised so much. In the months before the election was called then-Premier Pauline Marois made a flurry of spending announcements.

Former PQ finance minister Nicolas Marceau said the AG's report is based on departmental wishlists.

Marceau said it is unfair to assume a government will come through on all requests for financing or fill all its promises.

"We're talking about the concept of potential deficit, which is a deficit in which the government takes no action, makes no choices, makes no decisions, and I think this is absurd," said Marceau.

Even the premier admitted governments of all stripes can promise too much to win votes.

"I would not say that the PQ is the only government that increased its expenses just before an election, but the size of the increase is significant. We are talking about six percent of increase and roughly $5.7 billion dollars of deficit if nothing is done. But we will act," said Premier Philippe Couillard.

Finance minister Carlos Leito, who will present his budget on Wednesday, said his central message will be of shared responsibility.

"We all have to do it. Everybody is going to have to do his share so we can recover some freedom of action, protect our programs and move forward," Leitao said.