Billy Wright's father insists there is "firm and final" proof of state collusion in his son's killing.
He criticised the rules of the inquiry, which he said was not allowed to use the word "collusion".
Lord Maclean's report said there was no collusion with the killers.
David Wright said: "It looks like collusion, it sounds like collusion and in my mind amounts to firm and final proof of collusion by state agencies."
He said that culminated in the murder of his son.
Mr Wright has campaigned since his son's death for the truth.
He said the issue of how weapons were smuggled into prison was not properly addressed.
He added that a "fatal mistake" was made in not passing information to the prisons minister.
He said the service had been exposed for wrongful acts.
"It is appalling that in a democratic society that a finding has now been made that the (failure to pass on information) by the RUC of various threats against Billy Wright between 1996 and 1997 constituted dreadful acts of omission that facilitated his death," he added.