Mario Dumont, founder of the 14-year-old populist Action Democratique du Quebec told supporters east of Quebec City late Monday he was disappointed, the Globe and Mail reported.
"I would have liked to receive a better result. I assume full responsibility for that," he said. "And I will not be at the head of my party in the next general election."
The ADQ fell from 39 seats it won in 2007 to seven seats and attracted 16 percent of the popular vote, the Canadian Broadcasting Corp. reported.
Premier Jean Charest won a third term as his Liberals won 66 seats and 42 percent of the popular vote, while the separatist Parti Quebecois surged at the ADQ's expense. Under leader Pauline Marois, the PQ won 51 seats in the National Assembly in Quebec City with 35 percent of the popular vote, the CBC said.
A minor separatist party secured one seat in the 125-seat chamber.
Provincial election officials said 56.5 percent of eligible voters cast a ballot, which was the lowest turnout since 1927, the CBC said.