Liberal Leader Philippe Couillard says it's the turn of PQ chief Pauline Marois to answer questions following a report of an alleged illegal financing scheme within the party during the 1990s.
Montreal's La Presse newspaper reports the province's corruption inquiry is examining allegations of collusion involving engineering companies and the PQ.
Marois denies any wrongdoing and says she has no knowledge of such an arrangement.
Coalition party head Francois Legault, a PQ minister in the 1990s, also says he did nothing wrong and says he finds the media report troubling.
Couillard took the brunt of attacks on integrity issues earlier in the week.
He was grilled by the PQ 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.
During Thursday's leaders debate he was also attacked for his ties to Arthur Porter, a former hospital administrator who now faces fraud charges in connection with a scandal-plagued hospital contract.
Couillard and Porter ran a consulting agency together, and were appointed by Prime Minister Stephen Harper to the committee that monitors Canada's spy agency.
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