Originally elected as a member of Union Montréal, Perez sat as an independent councillor from December 2012 until August 2013, when he affiliated with the new Équipe Denis Coderre.
[9] He won a decisive victory beating his closest rival by over 20 per cent of the vote in his first election on November 1, 2009 running under the Union Montréal party of Mayor Gérald Tremblay.
In December 2010 he was named vice-president, and ranking member of the governing Union Montréal party, to the new Commission on the Examination of Contracts.
[13] Perez made Canadian news headlines[14] in May 2011 after he spoke up against the use of inappropriate Twitter remarks by a fellow councillor during council meetings.
Opposition city councillor Benoit Dorais posted insulting comments on his Twitter account about the Union Montréal members during a council meeting, some of which were directed at Perez.