Bloc Québécois Leader Gilles Duceppe walks by a Bloc pre-election campaign poster Tuesday after the first day of a two-day caucus meeting. (Jacques Boissinot/Canadian Press)

A federal election appears to be inevitable, Bloc Québécois Leader Gilles Duceppe said on Tuesday, as his party launched an ad campaign that claims there's little difference between Prime Minister Stephen Harper and Liberal Leader Michael Ignatieff.

"Mr. Ignatieff doesn't seem to look like he's going to back down, and Mr. Harper is not the kind of man who makes compromises or who achieves consensus … so I think the chances of an election are great — more than great," Duceppe said in Quebec City following a caucus meeting.

Last week, Ignatieff said the Liberals will try to trigger the defeat of Harper's minority Conservative government at the earliest possible date this fall. Harper would need the support of either the Bloc or the New Democratic Party to stay in power. So far, the NDP has been coy on its intentions.

Duceppe made his comments as his party unveiled print advertisements that target both Harper and Ignatieff, with the headline in French: Two Parties, One Vision, claiming neither is looking out for Quebec.

"We're talking about two parties who are trying to show themselves to be different, but when you look at the positions they've taken, one is saying the exact same thing as the other," Duceppe said.

Duceppe said both Harper and Ignatieff want to protect the oil sands industry, have refused to support loan guarantees for the forest industry and refuse to recognize the "Quebec nation in concrete terms."

"For us, there are two adversaries who are trying to distinguish themselves from each other but who have the same way of seeing Quebec, who are defending the same interests," Duceppe said.

"Of course, the Bloc is the only one that's different, and it defends Quebec's fundamental interest."

Speaking in Waterloo, Ont., Ignatieff said his party has brought out positive ads with a positive vision, unlike Duceppe, "who has started out with very negative ads."

"The Liberal party’s message is really quite simple. We want Quebec to be in the government of Canada. We want it to be at the centre of a good Liberal party, because the Bloc is sort of a permanent opposition."