“I didn’t know.”

It has been Mayor Gérald Tremblay’s stock response to reported misdeeds by members of his inner circle for the past decade.

However, a former political aide, Martin Dumont, testified this week before the Charbonneau Commission that Tremblay did in fact know, and that he deliberately kept himself in the dark about the details.

“I don’t need to know this,” Dumont alleges Tremblay said in 2004 as plans were being hatched inside his Union Montreal party to use huge illegal campaign contributions in a by-election.

Don’t-know has been Tremblay’s strategy from his first months in office, sources close to the mayor’s party have told The Gazette. In 2004, one person inside Tremblay’s party, then called the Montreal Island Citizens Union, said the mayor was clear about one point within his party after he was elected in 2001: he didn’t want to know what rules they were breaking.

The information, which the individual said did not come directly from Tremblay but rather from others within the party, could not be corroborated by The Gazette at the time.

The source made the disclosure to the newspaper after The Gazette published a report detailing more than $58,000 in catering and restaurant expenses, often including $100 bottles of wine, that the party charged to the city for reimbursement as research and secretarial expenses between January 2003 and April 2004.

Tremblay said at the time in a radio interview that he didn’t know about the expense claims and was furious. His party’s official representative, Marc Deschamps, said Tremblay ordered him to institute new rules within the party to prevent lavish expenditures on the public’s dime. The party also returned $11,804 of its reimbursed expenses to the city.

Since then, Tremblay has claimed he “didn’t know” a number of times.

He said it in 2011 when it was revealed the city’s comptroller-general had spied on the emails of the city auditor-general and Lachine borough mayor Claude Dauphin.

He said it in 2009, when it was revealed his former right-hand man, Frank Zampino, had vacationed on the yacht of construction magnate Antonio Accurso while Accurso’s consortium was bidding on a water-management contract, the largest in the city’s history, which it later won.

And he said it a second time in 2009, when a contractor redoing the roof on city hall alleged he was shaken down by a mafioso for a bribe for two members of the city executive committee.

Another former party insider told The Gazette Wednesday that around 2005 Tremblay refused to hear details about a security breach in which public safety had been compromised.

“He told me: ‘This conversation never happened’,” the former insider recounted of his attempt to complain to the mayor after learning details of the event had been held back from the public.

“He made it clear he didn’t want to know the details because he didn’t want to have to answer questions about it later. It’s his way of doing things.”

Dumont’s sworn testimony before the commission examining corruption in the construction industry dovetails with recollections of how things have operated within the party since the 2001 election.