MONTREAL—The dominant force in Montreal politics for the past decade is no more. On Thursday, the remaining members of Union Montreal admitted the party was beyond repair and resigned en masse.

After leading former mayor Gerald Tremblay to three terms in city hall, the party was hammered by a flurry of corruption allegations. Months of testimony at the Charbonneau Commission revealed a system of collusion that prospered during Union Montreal’s time leading the post-demerger city.

Despite the poisonous testimony on mainstream television nearly daily, the party’s death knell was sounded following Tremblay’s resignation last November.

Politicking in the fight to replace Tremblay split Union Montreal, elevating former executive committee chair Michael Applebaum to the post of interim mayor. New party leader Richard Deschamps was left at the head of a rump caucus, with a shattered brand.

Since then, the party has continued to shrink, losing borough councillors and mayors at a steady pace as they left Union Montreal to sit as independents. Many of the resignations came when entire borough delegations quit, most recently with Anjou in February.

On Thursday, Deschamps admitted Quebec’s anti-corruption inquiry had tainted Union Montreal’s name. The only solution was the party’s end.

“The testimony by different witnesses at the Charbonneau Commission in recent months has severely affected and badly tarnished the image of Union Montreal,” said Deschamps, surrounded by a small group of councillors.

“The current elected Union Montreal representatives have all agreed and decided to tender their resignations today.”

The party has filed for dissolution, leaving 38 former members of Union Montreal as independents at city hall, facing a bloc of 15 belonging to Louise Harel's Vision Montreal and another 10 sitting under the Projet Montreal banner.

The majority of the city's 46 borough councillors are also ex-Union-Montreal members turned independents.

Once the party pays off its debts, any monies left over will be returned to the City of Montreal’s consolidated fund.

“All members who are here today and are members of our caucus have every intention of completing their term,” said Alan DeSousa, a former chief lieutenant in Union Montreal.

Whether members of the party will run again in November, after a decade under Union Montreal’s banner, is still up in the air.

“Today I've resigned from Union. I still haven't decided what I’m going to be doing after the third of November,” said Helen Fotopulos, one of the founders of the party.

Union Montreal was formed following the forced municipal mergers, as a way for the former suburbs to maintain their autonomy as Montreal boroughs. The party won majorities in 2001, 2005 and 2009.

Robert Libman, former mayor of Cote-St-Luc, was there at the beginning and remembers the party as a grand coalition.

“It's sad to see the party go because I think it was a reflection of the face of Montreal. Sovereignists and federalists working together, Anglophones and Francophones, left and right. It was a very interesting dynamic with members of cultural communities. Now that vehicle has just evaporated,” said Libman.

Despite allegations of kickbacks and corruption, Deschamps said in the party’s final moments that Union Montreal had accomplished a lot for the good of the city. Something that he said has already been forgotten.