Mr Harris spoke to the media ahead of canvassing in Capel Street with Dublin Central candidate Paschal Donohoe.
Kieran Allen, who is a former lecturer and a member of People Before Profit, said that Mr Harris should be ashamed at the homelessness figures, which have risen to almost 15,000 people.
“You have got 4,000 children in this country who are homeless and it’s a direct result of your policies, and you should be ashamed of yourself,” Mr Allen said.
Simon Harris confronts heckler who told Taoiseach he ‘should be ashamed of himself’
Mr Harris said that when the eviction ban was in place, during the Covid-19 pandemic, homelessness did not fall.
Mr Allen said: “Are you joking, are you? You were told in the Dáil that if the eviction ban was removed, homelessness would increase.
“And don’t give me your ‘I am very concerned bit’, you actually voted to end an eviction ban.”
Mr Harris said everyone in Ireland is concerned about homelessness, but his main concern was the type of policies that would resolve the issue.
Earlier in the canvass, a passing cyclist shouted “gee-up, Sinn Féin” to which Mr Harris said “bring it on”.
In his comments to the media, Mr Harris said the cost of living was the number one issue people were raising on the doorstep, but that housing was also raised by people.
“There are real differences on the ballot in relation to housing, I will agree with my political opponents in relation to that, and there are different offerings in terms of the level of financial support that will be provided to first-time buyers.
“I’d say the number one issue coming up with me so far in this campaign is the cost-of-living challenges that people face. Housing remains a very serious issue.
“I’m having conversations with people that I feel are balanced, people can accept that there are more houses being built … but they also want to know about things like affordability. How can we scale that up?
“They also want to know, how can we actually get to a level of supply that we need to fix this crisis once and for all?
“And I really believe, and I think this is the difference between an election and Leaders’ Questions in the Dáil. In an election, it’s not good enough for the opposition just to critique our policies. They also have to explain theirs.”
He added: “Politics and housing deserves an honest debate in this election.”
Asked about comments made by former Fine Gael housing minister Eoghan Murphy that housing was not a priority during his tenure, Mr Harris said he was being “a little hard on his own record”.
“Eoghan Murphy did, during his time, establish the Land Development Agency, we did see the social housing fund restored, and we did see housing supply begin to increase.”
Minister for Public Expenditure Paschal Donohoe said that they had to ensure that “plans added up” when in government and said this has allowed them to invest in homes into the future now.
Fine Gael is pledging to oversee the construction of 303,000 homes between 2025 and 2030, with 75,000 of them social homes and 58,000 affordable or cost rental.
