The Irish Council for Civil Liberties has said the Referendum on Inquiries by the Oireachtas could turn Oireachtas Committees into 'kangaroo courts'.
The Council has launched a campaign advocating a No vote in next week's referendum.
Director Mark Kelly said the Referendum, if passed, would lead to a fundamental shift of power from the Judiciary to the Oireachtas.
He said that the consequences of such a development cannot be fully predicted.
Independent TD Catherine Murphy who is supporting the campaign said the proposed amendment is badly worded, open to abuse and rushed.
She said in the heat of a Presidential election people had little time to be considering the issues involved in the referendum.
The ICCL said the amendment provides no guarantee that the courts would have a role in reviewing the procedures adopted by the Oireachtas in the course of any inquiry.