Liberal leadership candidate Justin Trudeau slammed NDP Leader Thomas Mulcair's stance on introducing a new bill that would combine the NDP's Sherbrooke Declaration on sovereignty in Quebec with the Clarity Act, keeping the NDP's resolution to recognize a 50-per-cent-plus-one vote in any future referendum.

Speaking to reporters in Calgary, Trudeau said, "You cannot be half-pregnant on the question of Canadian unity … for me, it's absolutely unacceptable."

Trudeau was referring to the fact that while the NDP says it will oppose a Bloc Québécois bill to repeal the Clarity Act, the law that mandates a clear question and clear majority in any Quebec referendum, it has tabled an act of its own that upholds the 50-per-cent-plus-one majority for a vote on secession.

The NDP's bill, a private member's bill entitled an Act Respecting Democratic Institutional Change, was tabled Monday by NDP MP Craig Scott.

The bill would retain the Clarity Act's insistence on a clear question in any referendum, and would uphold the part that says that secession must be negotiated with other parties after a referendum in which 50-per-cent-plus-one of the Quebec population voted to separate.

NDP Leader Tom Mulcair (Adrian Wyld/Canadian Press)

Trudeau said that Mulcair and his "willingness to equivocate, his willingness to be open to a 50-per-cent-plus-one vote on sovereignty takes us back in a direction that we don't want to go, and it's a very careful political calculation by him to appease his strong nationalist base in Quebec."

Trudeau, a Liberal MP from the Montreal riding of Papineau, has a strong following among some federalist supporters in Quebec. If he wins the Liberal leadership, many think he might revive the Liberal Party's fortunes by appealing to the some of the soft nationalist vote that moved to the NDP in the last election.

Debate on the Bloc bill

Debate began Monday on a private member's bill sponsored by the BQ that seems designed, in part, to embarrass the NDP, which wrested away most BQ seats in the last election.

Bill C-457, an Act to Repeal the Clarity Act, was introduced in October by Bloc MP André Bellavance. In support of the bill, Bloc Leader Daniel Paillé wrote a letter to all the party leaders except the Green's Elizabeth May, arguing that since they voted to recognize the Quebec people as a nation in 2006, they must realize that a nation has the right to decide its own destiny in its own way.

BQ MP Andre Bellavance, right, has introduced a private member's bill to repeal the Clarity Act. (SRC/CBC)

In debate Monday, Elizabeth May said, "Every party, other than the Green Party, supported a motion that Quebecers are a nation, and today you are all hoisted with your own petards."

The Clarity Act, passed in 2000, was the government's response to the knife-edge margin in the 1995 referendum in Quebec that saw the province come close to beginning the process of splitting from the rest of Canada.

The Clarity Act gives Parliament the authority to decide whether any new referendum on separation contains a clear enough question, and whether any vote is the expression of a clear majority of the will of the people of a province. It further states that secession cannot take place without negotiation with the federal government and the other provinces, as well as First Nations.

The NDP voted in favour of the Clarity Act in 2000, although NDP MPs Libby Davies and Svend Robinson voted against it.

NDP backs '50-plus-1'

The party is on the hot seat now, because in 2005 it adopted its Sherbrooke Declaration, which states the NDP would recognize a 50-per-cent-plus-one vote in a referendum on the political status of Quebec. The declaration was part of the NDP's attempt to make significant inroads into the province of Quebec, which it saw as its path to eventually forming government.

Speaking in defence of the Clarity Act, its author Liberal MP Stéphane Dion asked if 50-per-cent-plus-one is a clear majority, then what could be an unclear majority?

In the 2011 general election, the NDP won 58 of Quebec's 75 seats, and the Bloc was reduced to just four. It was a stunning transfer of power from one party to another, but the Bloc has been buoyed lately by the Parti Québécois' minority victory in the recent Quebec provincial election.

The introduction of a bill that has no chance of passing may be its first shot in flushing out the views of the NDP on whether it backs its own Sherbrooke Declaration or supports the Clarity Act.

Although the Sherbrooke Declaration firmly states that a majority is 50-per-cent-plus-one, the Clarity Act does not define what a "clear majority" means.

The new bill tabled Monday by the NDP will state that 50-per-cent-plus-one is a clear majority, if the vote count has been done correctly.

In deriding the NDP bill, Trudeau said it's "yet another example where co-operation between the Liberals and the NDP in the coming years is out of the question for me."