Three municipal politicians resigned Monday from Montreal mayor Gérald Tremblay's political party, citing irreconcilable differences over his leadership.

Downtown Ville-Marie borough mayor Benoît Labonté was the first to announce his departure from the Union Montréal party, and issued a harsh critique of Tremblay's leadership.

"Nothing has been done," about key downtown issues of late, Labonté said. "After a few months I must admit [it], and I'm sad."

Tremblay took control of the downtown borough after the August crisis at the Bay department store, where engineers found several fissures in concrete support beams connected to the underground tunnel.

That and the slow pace dogging the city's plans for an entertainment district became too much to bear, Labonté said.

He will maintain his position as borough mayor but said he's also considering his future tack.

Borough councillor Karim Boulos also announced his defection Monday over leadership differences with Tremblay. "As an elected official, I made a commitment to serve the population of Ville-Marie, not simply toe the party line," he said.

Municipal councillor Soraya Martinez of Saint-Michel was the third to go. "It was a falling out waiting to happen," she said.

Tremblay said the departures came out of the blue and his leadership at city hall remains strong.

"What's surprising is that two weeks ago, when I announced responsibility in major projects in the downtown core, [Labonté] said clearly he was in agreement with this decision. He recognized my leadership. He said he would be beside me at the election in 2009."

All three politicians will sit as independents.