Queenslanders may never know why 26 bikie gangs have been declared criminal organisations.

Attorney-General Jarrod Bleijie says police evidence and detailed criminal histories are behind his declarations.

But the details have been kept secret because making them public could jeopardise police operations or public safety.

Legal experts say they may never be made public or tested in any court, and that because the bikie gangs were never allowed to hear the evidence, they can’t challenge it in court.

Australian Council for Civil Liberties president Terry O’Gorman says not even a judge can hear the evidence against an accused criminal organisation.