Stephen Harper once tried to form the type of coalition government he's now calling illegitimate and unprincipled, Bloc Québécois Leader Gilles Duceppe said Saturday as he launched his election campaign.

Duceppe slammed Stephen Harper for his criticism of the opposition over trying to work together.

"He finished second in that election," Duceppe said in Montreal. "If he says that's undemocratic, well, that's exactly what he was asking for. So let's not play games with history. He has to take responsibility."

Duceppe says Harper called him and Layton to a meeting in Montreal in 2004 where they came up with new rules — rules now in use in the House of Commons — for running committees and some debate days.

"It was one of the most important meetings I had with respect to parliamentary democracy. And I'm not rewriting history here … we changed most of the rules of the House that day," Duceppe said. "They were important changes."

Duceppe pointed to the letter he signed with Harper and Layton that said Harper was ready to form a government if then-prime minister Paul Martin lost the confidence of the House.

Harper has argued a coalition is not a legitimate or principled way to form government, and he's pointed to the Bloc in particular, arguing Liberal Leader Michael Ignatieff shouldn't consider relying on the support of separatists.