The Simon Communities of Ireland say homeless services need to be coordinated between groups such as theirs and other homeless charities.
It comes amid claims that a proliferation of such groups - who provide food, sleeping bags and tents to rough sleepers - are hindering the work of established organisations.
Wayne Stanley is head of policy and communications at Simon Communities Ireland.
He told Newstalk Breakfast a structure is badly needed.
"There has been a huge growth and they're all over the country - and it's people of goodwill who are going out to try and support and address the crisis that they're seeing on their streets and in their towns.
"From a Simon Community perspective, I think we have to acknowledge that the Simon Communities were set up by volunteers - that volunteers make a huge contribution to the work of the Simon Communities."
But he says people need to be pointed in the right direction.
"I think the piece that's definitely missing is we need some kind of coordination to make sure that - where people are meeting people that are maybe in distress - that they know where to send them.
"We all work together across the Simon Communities, Focus Ireland, Peter McVerry - and we know what services we all provide and how to direct people to get the best service."
He says some people have been met by a number of different organisations.
"What we need to do is make sure that if somebody is doing that, that there is some kind of an overarching structure around it.
"That make sure that instead of engaging with somebody who's vulnerable, they're actually making us aware that they are there and the professional staff can go out and attend to them".
He says while there is room for everyone, this needs to be properly managed.
"I do think there is a place for volunteers.... but what we need is a structure and a system by where they can do the very best for people and harness that goodwill that's out there."
And he says 'at its most extreme', some groups could inadvertently be keeping people on the streets.
"What I want to do is acknowledge that a lot of people who volunteer do it with the very best of intentions, but there is always a risk when you're pulling people away from services that that person will spend longer in homelessness".