There are concerns the issue could once again return to the forefront if the sovereigntist Parti Quebecois win the next provincial election, which could come as early as this fall.
The Harper government, which holds only five seats in Quebec, has a limited presence in the province and no clear spokesperson to make the case for federalism in a debate over the country's future.
NDP Leader Tom Mulcair said the secret meeting with Mulroney is another sign that Harper is out of touch with Quebecers — and hasn't made efforts to reach out like the New Democrats have.
"Every time Mr. Harper has had an opportunity to give real meaning to the recognition that the Quebecois form a nation within a united Canada, he's said no," said Mulcair, who was in Hudson, Que. for a ceremony naming a park in honour of late NDP leader Jack Layton.
The Canadian Press revealed Friday that Harper held a secret meeting in a Montreal hotel with the former prime minister earlier this month for advice on how to build a better relationship with Quebec.
Harper sought similar advice that same day from Liberal Premier Jean Charest, government sources said.
The Quebec Liberals, though, are in trouble themselves. An election could be held in early fall and the winner is far from certain. A recent provincial by-election in Quebec saw the Parti Quebecois win a riding that's been held by the Liberals for 46 years.
PQ Leader Pauline Marois said Harper is right to be concerned, and that Quebecers are fed up with a federal government that doesn't represent their interests.
Citing a laundry list of moves ranging from abolishing the gun registry to changes to environmental regulations, Marois labelled the Harper government "anti-Quebec."
Marois, though, added that Harper was right to reach out to Mulroney, who she said understood Quebec and tried hard to address the constitutional question.
"He knows Quebec quite well, at least better than Mr. Harper," she said.
Harper will be in Quebec on Sunday for a Conservative rally aimed at reviving the party's floundering fortunes in the province.
The advice Harper received from Charest and Mulroney is expected to figure prominently in the prime minister's speech, where he will seek to remind Quebecers of his commitment to giving greater powers to the provinces and his respect for Quebec's place in the federation.
Mulcair, though, said the damage for Harper was already done.
"Quebecers have taken notice," he said. "There's no way for him to change what he's done in the past."'
— with files from Marie-Michele Sioui
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