Former prime minister Jean Chretien says he's disturbed by the NDP's "ambiguity" on national unity and its willingness to resurrect the debate over the Constitution.

He was referring to an NDP caucus that suddenly includes sympathizers of Quebec independence and is the first pan-Canadian party to oppose the Clarity Act, Chretien's landmark law which sets rules for a future referendum.

"Obviously, there's some ambiguity and I see they've started to talk about the Constitution again since the election," Chretien said during a visit to Quebec City.

"I said in 1993: 'If you want to talk about the Constitution, vote against me because I won't go there. There are other problems than that."'

Jack Layton has said the NDP would support a simple majority win in a sovereignty referendum.

The NDP stance would seem to be at odds with the Clarity Act, which calls for a clear majority for sovereigntists before Ottawa would entertain negotiations to break up the country.

The law also insists that the federal Parliament have a say over whether the Quebec's referendum question was sufficiently clear.

With the sovereigntist Parti Quebecois leading in the polls and hoping to return to power within two years, such questions are not necessarily hypothetical. The NDP's position has taken on an added importance because, with 59 seats in the province, it is now Quebec's voice in Parliament.

Chretien says he wants to know where the new NDP members stand.

He described as "original" an idea by Stephane Dion, the father of the Clarity Act, who said the new NDP MPs should declare their loyalty to Canada.

"Me, I didn't have to do that," said Chretien, who was prime minister between 1993 and 2003, referring to the fact that his troops were unequivocally federalist.

"I don't know what Mr. Dion said, but he has a lot of ideas. He was one of my ministers for 10 years."

At least two Quebec NDP MPs elected have said they wouldn't know who they would support in another sovereignty referendum. One recently said he is still a sovereigntist.

Chretien was attending a meeting of the InterAction Council, a group of 20 former world leaders who gather to discuss key world issues.

Ex-U.S. president Bill Clinton and ex-Mexican president Vicente Fox are among those in attendance.