Nycole Turmel was named interim leader of the NDP last Thursday by Jack Layton, who went on a leave of absence for cancer treatment. She is a Member of Parliament for a Quebec riding, or district.
In the meantime, it emerged she has been a member of the NDP since 1991 but also joined the separatist Bloc Quebecois Party in 2006 to support a friend who was running, the Canadian Broadcasting Corp. reported.
She also acknowledged being a member of Quebec Solidaire, a provincial separatist socialist party.
NDP officials told reporters they didn't permit members to belong to more than one federal political party but were confident Turmel wasn't aware she was violating policy.
In an interview with the CBC, Turmel played down her separatist party affiliations.
"I am a federalist, I represent Canadians," she said.
Meanwhile, Conservative Prime Minister Stephen Harper told reporters Wednesday in Hamilton, Ontario, the NDP's choice of an interim leader with a separatist history was "disappointing" to Canadians.
"I think Canadians expect that any political party that wants to govern the country be unequivocally committed to this country," Harper said.