Prof Dermot Walsh's comments follow concerns raised by the Human Rights Commission early this month about the effectiveness of the body as outlined in the General Scheme of the Garda Síochána Bill.
Last Friday, the chairman of the Garda Síochána Complaints Board, Gordon Holmes, said the inspectorate, which will replace the board, had to have all the necessary powers including the power to compel gardaí to answer questions for it to work.
Prof Walsh, director of the Centre of Criminal Justice in the School of Law at the University of Limerick, also criticised the proposal to have three people, rather than one person, heading the inspectorate.
"The whole bill, or scheme of the bill, is very disappointing, particularly in relation to complaints procedures," he said.
"I don't think they are going to make much difference to the abject failure of the current complaints provisions to tackle police malpractice."
He said the detail of the scheme shows that very little would change from the current process whereby the Garda Complaints Board must ask the Garda Commissioner to provide an officer to investigate a complaint against another garda.
"Under the new arrangements, complaints against gardaí will continue to be dealt with by the police themselves," said Prof Walsh.
Under the draft bill, the inspectorate only has to investigate complaints involving death or serious injury.
The inspectorate can refer all other complaints to the garda commissioner.
"There are no absolutes. Even in cases of death or serious injury, it is open to the inspectorate to call on the commissioner to provide members to assist with the investigation.
"It is quite possible that all complaints will continue to be dealt with by the police themselves."
The Human Rights Commission, while generally supportive of the proposed inspectorate, has also raised concerns about the new bill.
It said the inspectorate did not have the same powers as a garda to arrest and hold suspects, even in cases of death or serious injury.
"It is therefore possible to perceive a case involving serious allegations of wrongdoing where, given the inadequate powers ... the Inspectorate may feel compelled to refer the case to the Commissioner for a more thorough and effective investigation to be carried out."
The HRC said this situation "could seriously undermine the effectiveness of a complaints body" and recommended that the inspectorate be given the same powers as gardaí.