MONTREAL - Former union boss Jocelyn Dupuis was back on the hotseat at the Charbonneau Commission Monday, where he attempted to explain the timeline of his departure from the FTQ-Construction union.

Images revealed at the commission of FTQ leaders partying with construction magnate Tony Accurso in the Virgin Islands proved embarrassing for Dupuis, who nevertheless said he had no problem defending the ethics of a union leader accepting such lavish gifts from an employer.

“In my mind, we were celebrating a success story,” he said. Dupuis proved more defiant when asked about his sudden departure from the FTQ-Construction wing in the fall of 2008.

His first story on the stand was about stepping down one year after being elected in order to make room for a new generation of union leaders.

“We had all agreed on some kind of new generation of leaders, with directors from the outside,” he said.

His temper flared, however, when confronted with evidence that he was pressured to resign because of his excessive expense account claims, and that he was still trying to influence union leadership after his 'retirement.'

“That's not what happened, Mme. President. I'll explain from the beginning -- and I'll try keeping my cool,” he told Justice France Charbonneau.

“You’d better keep your cool,” Charbonneau fired back.

Dupuis then admitted the expense-account scandal was the real reason he left FTQ-Construction.

“No way I'm going down alone,” he testified.

Wiretaps, however, show that months after his departure, Dupuis was still calling FTQ president Michel Arsenault – who stepped down Monday amid his own controversy – to talk business.

Dupuis needed Arsenault to influence the FTQ-Solidarity Fund so it could invest in Mafia-related companies.

When Arsenault told him no in 2009, Dupuis blackmailed him.

“I'm going to denounce you. I'll denounce everyone. I'll reveal everything I know,” Dupuis was heard threatened on the wiretaps.

Arsenault then backed down, agreeing to organize a meeting on the matter.