She went after the perceived front-runner during a leadership debate Saturday, questioning whether he has any real understanding of the problems facing middle-class Canadians.
"You keep referring to the middle class but you yourself have admitted you don't belong to the middle class. I find it a little challenging to understand how you would understand the challenges facing real Canadians," Hall Findlay said to Trudeau, during one of the debate’s one-on-one exchanges.
Trudeau responded that his privileged background isn't an issue, what matters is his commitment to public service.
Hall Findlay was booed by some in the debate audience and was widely criticized on social media for the aggressive questioning.
She said she was trying to question Trudeau about whether his experience qualifies him to be leader.
Other candidates, including Deborah Coyne and Marc Garneau refused to mount similar attacks on Trudeau.
"Let's not be petty Canada. Anybody in this country who wants to run for the leadership of this country should not be looked down upon in any way, whatsoever, regardless of their financial income," Garneau said.
After the debate, Hall Findlay said her comments were not personal and on Sunday she went further by posting an apology on her website.
"There are some who believe that I overstepped a line in the leadership debate," the statement said. "To Justin, his family and to those who were offended, I apologize."
"My comments were not meant to be personal, in the sense of being in anyway a comment on Justin's character -- indeed, I have the greatest respect for Justin's passion, enthusiasm and commitment."
Trudeau's campaign didn't respond to the apology.
Nine candidates are vying to become the party's new leader, which will be selected on April 14.
The candidates include Garneau, Trudeau, and Joyce Murray, former MPs Findlay and Martin Cauchon, lawyers Deborah Coyne, David Bertschi, and George Takach, and retired Lt.-Col. Karen McCrimmon.