The Munk leaders' debate on foreign policy will be bilingual, but it will be up to the leaders themselves to decide how often they'll speak in each of the official languages, organizers said Monday.

And yet the revamped format still might not be enough for the Liberals and the NDP, who last week criticized debate organizers for not giving equal time to English and French.

"Our final proposal allows debate participants to speak in either official language when they want, and for as long as they want, throughout the debate," Rudyard Griffiths, chair of the Munk Debates, said. "Simultaneous translation will be available for the entire debate proceedings."

The parties have until noon Tuesday to accept the new terms of the debate or forfeit their position on the stage.

"The debate's approach to the use of French and English is identical to that of the House of Commons," Griffiths said. "We believe that an event organized along these lines more than satisfies the request that the debate be bilingual."

NDP, Liberals waffling on debate participation

But, despite the changes, it appears the NDP is now considering whether to pull out of the debate entirely, which is scheduled for Sept. 28 in Toronto.

"This isn't Parliament," said one NDP adviser, who added the party had agreed to a debate that was "fully, equally bilingual."

The adviser added the New Democrats were concerned that Griffiths, who will serve as moderator, may not himself be fluent enough in French to ensure a free-flowing conversation in that language.

The Liberal Party, for its part, did not immediately accept the new terms of the debate. A party official says it was reviewing the new proposal and would be providing a response soon.

Griffiths told CBC News that this is the final offer to the parties. "Our debate is only two weeks away. At this point, we need to know who is going to be debating and if we're going to have a debate at all," Griffiths said. "We'll know by noon [Tuesday]."

Even if one of the parties pulls out, Griffiths said the Munk Debates would be willing to go ahead with a one-on-one debate with any combination of leaders.

As for the criticism that he is not up to the job given his lack of fluency in French, Griffiths said it shouldn't to be an issue given all of the proceedings will be simultaneously translated.

Liberals, NDP raise red flags

The format change comes after the Liberal Party last week threatened to pull out of the debate if organizers didn't agree to a fully bilingual format.

Griffiths had initially said the debate would include "bilingual components," and that about 20 per cent of the proceedings would be in French.

"We agreed in principle, under the presumption that this was a bilingual debate; however, this is clearly not a bilingual debate," wrote Dan Gagnier and Katie Telford in an open letter to Griffiths last Wednesday.

The NDP also raised red flags with the proposed format. "It was Tom Mulcair's leadership that ensured there would be a balance of both languages in the leaders' debate," Brad Lavigne, senior campaign adviser, said after details of the initial format were released.

"We firmly stand by our criteria for complete equality of French and English."

Opportunity for one-on-one debates

The debate itself will consist of six "major" segments, devoted exclusively to foreign policy. Each segment will begin with a question from Griffiths to one of the leaders.

Leaders will have 90 seconds to answer before engaging on a one-on-one debate with another leader for seven minutes. Then the third leader will join the debate for another five minutes.

Griffiths will ensure each party leader gets roughly an equal amount of time during the debate.