The Justice Minister earlier offered an olive branch to judges amid objections to the controversial bill
The Dáil has been told that a new bill to overhaul the nomination of judges is "a really bad piece of legislation".
Fianna Fail has insisted the overhaul is being driven by "one or two members of Government who really don't know what they're talking about".
The party says it will oppose the controversial bill, which will give lay people a majority of the seats on the group that chooses judges.
Fianna Fáil's justice spokesperson Jim O'Callaghan says the bill is misguided and poorly constructed.
He argued: "We think it is bad for the administration of justice. We think it is bad for for the Irish public.
"It hasn't been carefully thought out," he added.
Earlier, the Justice Minister offered an olive branch to judges, by agreeing to let the heads of more courts have a seat on the new body to pick the judiciary.
Charlie Flanagan says the move is being made "after careful consideration" of an intervention made by judges yesterday.
He made the announcement as he began the Dáil debate on moves to create the new Judicial Appointments Commission.
The commission would introduce a lay-chairperson and a majority of lay-members.
The Chief Justice and the heads of the other courts wrote directly to the Taoiseach outlining concern about the plans, while the association representing judges in Ireland warned that the proposed changes are “seriously flawed.”
Minister Flanagan says the moves will make the system fit for purpose - but accepts that the presidents of the Circuit and District Courts should be included.
He told deputies: "Having listened to the views of the judiciary on the matter, and reflecting on the point in the context of pre-legislative scrutiny debate... it seems to me to be desirable to meet this particular point."
He added: "The new Commission will have strong lay representation. This legislation is largely about getting the balance right as between different contributions and interests.”
Transport Minister Shane Ross has frequently called for reform of the appointment process, and has called the current system “rotten".
Minister Flanagan is known to have reservations about certain aspects of the legislation – and is reportedly unhappy with some of Minister Ross’s comments on the matter.