According to Mr Justice Patrick J McCarthy, proposed changes will do long-term harm to the administration of justice.
Under planned legislation sought by Transport Minister Shane Ross last year, the nomination of judges will be placed in the hands of an independent body with a non-legal chair.
The bill has been widely criticised by the judiciary.
Mr Ross also made headlines when pushing for the legislation by making a number of comments critical of judges.
Mr Justice McCarthy’s remarks came in an address to solicitors receiving parchments at the Law Society in Dublin.
In a strongly worded address criticising the proposals, he warned of long-term harm to the administration of justice in Ireland.
He said concerns of Chief Justice Susan Denham should be taken with “with the utmost seriousness” by the Cabinet but were not.
Mr Justice McCarthy also hit out at the chief justice’s exclusion from the appointments commission.
“In particular, the exclusion of the Chief Justice from the chair of the Government’s proposed appointments commission downgrades or marginalises that office and is not in accordance with that respect,” he said.
“It would be hard to see how, in principle, in a matter of fundamental importance to the Government or the Oireachtas, the Taoiseach, Cathaoirleach, or Ceann Comhairle would be downgraded from the chair of any similar body or that, that approach would be considered for an instant.
“The fact that only one other judge will be a member of the commission and others present on sufferance, only on an occasional advisory basis, is further evidence of that lack of respect.”
Mr Justice McCarthy said the proposals are not in accordance with international principles about judicial independence.
He said that while lay members can bring “useful insights”, they would not be able to make more than a “limited contribution”.
The commission as a whole, he said, must be in a position to assess the larger needs of the administration of justice in the long term both strategically and in terms of a particular requirement for a judge with a particular expertise
He added: “It will not have the competence to do that if the majority are lay members; the Chief Justice is not in the chair and all of the Presidents of the Courts are not full members — it is hard to envisage any system of appointment in any walk of life which would give dominance to those with little or no expertise of the essential criteria for appointment.”