Nycole Turmel's NDP colleagues say they're surprised she had memberships in sovereigntist parties but believe her when she says she's a federalist.

Turmel was forced on the defensive  less than a week after being confirmed as interim NDP leader when it emerged Tuesday she had been a member of the Bloc Québécois until January. She also confirmed she still held a membership in a leftist provincial party that supports sovereignty, which the NDP later said she would cancel.

Turmel, who is leading the NDP while Jack Layton takes time off to fight cancer, says she took out the Bloc membership to support an MP friend. She says she supports some of the party's policies but not its push for Quebec to separate from Canada. Turmel says she is a federalist.

NDP MPs Wayne Marston and Rathika Sitsabaiesan, answering reporters' questions at a news conference, said they were surprised to learn of Turmel's memberships in the pro-sovereignty parties.

"I hadn't been aware of it, and I think that was a normal reaction," Marston said.

Sitsabaiesan categorized the revelation as "water off our backs."

"Her ties with the NDP are long-rooted and strong ties," she said. "She's held leadership roles over many years. She's been a member of the party for 20 years."

Marston says Turmel has a stellar reputation in the labour movement and points out she ran for a federalist party, not for the Bloc.

"I take her at her word …she has a reputation of directness and forthrightness, and I'm quite satisfied with that," he said.

Prime Minister Stephen Harper says he found Turmel's Bloc and Québec Solidaire memberships disappointing.

"I think Canadians expect that any political party that wants to govern the country be unequivocally committed to this country," Harper said in Hamilton, Ont. "And I think that's the minimum Canadians expect."

Liberal MP Geoff Regan says he believes the memberships indicate this was not just a flirtation, but a long-term relationship with sovereignty.

"You have to ask yourself how naive do you have to be to actually join two separatist parties and then believe that you can run for a federalist party and become its leader?" he said.

Turmel, elected May 2 for the first time, was voted caucus chair and then elevated to interim leader when Layton announced last week he was taking several weeks off. He said he expects to be back when the House returns Sept. 19.