Speaking to Ryan Tubridy on last night's Late Late Show, he said the sit-in at Apollo House was "an act of civil disobedience"
Oscar-winning singer-songwriter Glen Hansard said homelessness charities "do not need to exist" as a sit-in at an unoccupied Dublin building continues.
Speaking to host Ryan Tubridy on the Late Late Show on the ongoing Home Sweet Home coalition, he said the money raised for charities goes "immediately into the air" and is "swallowed up".
Home Sweet Home have taken over Apollo House on Tara Street, and are in the process of converting it to shelter those who face the prospect of sleeping rough this Christmas.
According to the Irish Times, there are currently five homeless families in the building and "more will follow".
He called his actions, along with those of several artists including director Jim Sheridan and singer Hozier an "act of civil disobedience".
"Can you imagine walking home Christmas Eve after doing your shopping and seeing no homeless people on the street?"
He added that there will be a call-out for volunteers in the future and said he wanted the government and Nama to get behind the "radical" idea.
The campaign has received backing from Sinn Féin's Peadar Tóibín saying: “I admire the inventiveness and drive behind the ‘Home Sweet Home’ campaign.
"I wish this project all the best and it is my hope is that the government will follow suit and put the many buildings and acres of land lying idle around the country to good use – and build the homes that are so badly needed in this state."
Campaigner Fr Peter McVerry applauded demonstrators, but stressed that the occupation was "not the solution" to homelessness crisis.
"I have no problem with them taking over the building. However, it's not the solution to the homeless crisis; that's my difficulty and that's why I won't join them," he said.