In an interview with Evan Solomon, host of CBC Radio's The House, Landry said Harper has been aninvoluntary ally of the Parti Québécois.
The issue of sovereignty has become one of the main issues of the current provincial election campaign in Quebec, although Harper refused to weigh in on it earlier this week when reporters asked him about it during a trip to South Korea.
Landry was premier of Quebec from 2001 until 2003 and led the Parti Québécois from 2001 to 2005. Now, he says Conservative policies are doing the work of the PQ for the party.
"When Harper is promoting monarchy and British monarchy in an excessive manner, when Harper is promoting reactionary policies on the international scene, without wanting to help us, of course, [he] did it anyhow," Landry said.
"When you promote almost in a fanatical way the British monarchy in Quebec, you're helping the independence of Quebec," he said.
Landry has been known for making controversial comments in the past.
Landry also said he agrees with the NDP's "Sherbrooke Declaration" which states that the party would recognize a 50-per-cent-plus-one vote in any future referendum, and that Liberal Leader Justin Trudeau is "apparently, and I say that in respect, very superficial."