MONTREAL -- The Parti Quebecois faced questions of its own about tax havens and corruption on Saturday as integrity issues took centre stage in the provincial election campaign.

Liberal Leader Philippe Couillard said it's the turn of PQ chief Pauline Marois to explain herself following a report of an alleged illegal financing scheme within the party during the 1990s.

Montreal's La Presse newspaper reported the province's corruption inquiry is examining allegations of collusion involving engineering companies rewarded with public contracts in exchange for party donations.

Marois denied any wrongdoing and said she has no knowledge of such an arrangement.

"I have never heard anything about that," she told reporters.

Coalition party head Francois Legault, who was a PQ minister in the 1990s, also said he did nothing wrong and added he found the media report troubling.

In recent days, the PQ has tried to focus on integrity and identity issues and away from talk of another referendum, something polls suggest a majority of Quebecers don't want.

Until now, Couillard has been the subject of the brunt of attacks.

During Thursday's debate Marois hammered away at Couillard's past ties to Arthur Porter, a former hospital administrator who now faces fraud charges in connection with a scandal-plagued hospital contract.

He was also grilled by political opponents following a Radio-Canada report that he placed $600,000 in an offshore tax haven while practising as a neurosurgeon in Saudi Arabia well before embarking on his political career.

Couillard has said there was nothing illegal about the account and that he paid taxes on the money in it upon his return to Canada.

On Saturday, it was the PQ's turn to face questions about favourable tax arrangements.

Quebec Solidaire, a small, social democratic party, called on PQ candidate and media mogul Pierre Karl Peladeau to explain why more than 60 companies that appear linked to Quebecor and its subsidiaries are registered the state of Delaware.

Peladeau is the majority owner and former CEO of Quebecor.

Amir Khadir, a spokesman for Quebec Solidaire, pointed out that Forbes magazine has qualified Delaware as one of the world's top tax havens.

"This is unfair and unacceptable," he said at a news conference.

"A company cannot operate like that."

Peladeau told reporters later in the day he has done nothing wrong.

He said companies hoping to do business in the U.S. must be registered in the country.

"There's no particular advantage to being incorporated in Delaware," he said.

The PQ said in a statement Quebecor's head office remains in Montreal and the company pays the bulk of its taxes in Quebec.

With files from Lise Millette and Melanie Marquis in Montreal and Julien Arsenault in Cacouna