The Peter McVerry Trust says tents are not a safe solution to rough sleeping.
It comes as a homeless man remains in a serious condition after he was injured when his tent was taken away in Dublin on Tuesday.
He was sleeping when it was removed from the banks of the Grand Canal during works by Waterways Ireland and Dublin City Council.
Pat Doyle - who is the CEO of the Peter McVerry Trust - said when people are in tents, it is hard to know how they are.
He said: "You can't see how people are doing, they're not visible to you when they're in a tent.
"I experienced that myself when we went out to check the numbers late last Tuesday night.
Gary is a soup kitchen volunteer and knew the man - he explains why people are opting to live in tents.
He said: "They try to keep to themselves as much as possible.
"The reason they're in these tents along busy areas is because when they're in quiet alleyways they're in danger of being set on fire or...
"This has happened, it's been reported in the news before tents being set on fire or tents being vandalised while people are in them."