Forum spokesperson Dr Oliver Sutherland said the college knew what was going on because he spoke to its annual meeting about it in 1977.
He said the college had neglected to raise concerns about the abuse despite being aware of it for the last 50 years.
''Far from totally remaining silent they actually praised Dr Leeks and his work at Lake Alice and endorsed it and in that regard in our view were complicit in the abuses and the torture of the children at Lake Alice.''
Sutherland said it was a case of members of the medical profession sticking together.
''Bit of an old, probably white, male club and so they don't like to speak out publicly against one of their members.
''I think they have just stuck together and decided to either endorse him or just say nothing.''
A report written by psychiatrist Dr D.G McLachlan in 1977 praised Leeks.
Sutherland said it appeared that report had influenced police not to lay charges at the time or since.
''Dr McLachlan was a fellow of this Royal College and so he clearly spoke with their authority and he was fully briefed. The police gave him all of their notes relating to their 1977 inquiry and asked for his view on them, so he knew - perhaps better than anybody - what was going on at Lake Alice.''
Sutherland said the college had indicated it was willing to discuss an apology, but not until the inquiry reported back on Lake Alice next year.
He said this was not good enough and he wanted action before the end of this year.
''We are pleased they will meet and we can sit down and talk through with them how they might frame their apology.
"In terms of the timeline, I am concerned about that. Every day that passes the survivors of Lake Alice are getting older and fewer in number, and so we need to push it along faster than the Royal College seems to be indicating.''
RNZ has approached the RANZCP for comment.
Sutherland said survivors would welcome an apology even at this very late stage.
''Survivors have waited a long time to get any justice for what happened to them when they were children at Lake Alice, so I think the apology will mean something and at any rate it will be one way for the Royal College to atone for their failure to act in the past.''
Sutherland, who was a witness at the Royal Commission into Abuse in Care's Lake Alice inquiry earlier this year, said he had no doubt its findings on the Lake Alice Child and Adolescent Unit would condemn the regime that was in place at Lake Alice under Leeks in the early 1970s.
''They will condemn it and I am sure they will find, as did retired Justice Rodney Gallen (in 2001), that it was outrageous in the extreme.''
- RNZ
