Children as young as 12 have been given alcohol and drugs by Occupy Melbourne protesters, the Salvation Army says.
Major Brendan Nottle, its commanding officer for Melbourne, said 12- and 13-year-olds had told youth workers they had sniffed glue at City Square when the protesters were camped there last month.
Other children aged 15 and 16 had said they were given alcohol, while another spoke with youth workers after using marijuana given to him at City Square.
In another case, people involved in the protest took two 16-year-old girls to a house, where they got drunk, Major Nottle said.
Victoria Police has now revealed the concerns were one reason it moved to evict the protesters from the City Square.
Major Nottle said the Salvation Army supported the protest but was concerned about the safety of vulnerable people, including wards of the state and homeless youths, who became involved.
He said the concerns were not limited to the occupation of City Square: the army was continuing to hear stories about drug and alcohol use in the current protest site at Treasury Gardens.
'Our interaction with the people from Occupy Melbourne is they're good people, we've got no issue with them, but I think they're unaware just how vulnerable some of the young people are that are accessing the Occupy Melbourne site,' he told AAP.
Major Nottle said the army raised its concerns with Melbourne City Council, the Department of Human Services and police, as well as Occupy Melbourne representatives.
Police and DHS workers removed seven wards of the state from the camp set up at Edinburgh Gardens last week, he said.
Victoria Police Superintendent Rod Wilson said while he was not pinning the blame on genuine Occupy Melbourne organisers, 'they don't know half the people who are in those spaces'.
'They're not in control of whoever comes in and says I want to be part of your movement' And who's doing the check to see if that person's OK to deal with young people?'
Occupy Melbourne spokesman Sam Castro said the group was taking the claims seriously and aimed to care for youth and the homeless who visited the protest.
'Occupy Melbourne has a strict no drugs, no alcohol and no violence policy and we are shocked at the claim that have been made today,' Mr Castro said in a statement.