The Seanad Committee on Selection, which appoints members to committees, has recommended that Independent Senator Sean Barrett and Fianna Fáil's Marc MacSharry sit on the banking inquiry.
The Government nomination of Labour's Susan O'Keeffe was not accepted by the committee.
Mr Barrett was selected unanimously, while Mr MacSharry was accepted by five votes to three.
Ms O'Keeffe was rejected by four votes to three after one abstention.
The chairman of the committee is expected to bring the recommendation to the full Seanad to accept, reject or amend it.
If accepted, it would mean the Government would lose its majority on the inquiry.
Government sources said this evening that the recommendation would be voted down.
Two Government senators and an independent senator, who normally supports the Government, were not present at the meeting.
The nine-person inquiry will be chaired by Labour TD Ciarán Lynch.
The other members are Sinn Féin's Pearse Doherty, Fine Gael's Eoghan Murphy, Kieran O'Donnell and John Paul Phelan.
Michael McGrath will represent Fianna Fáil and independent TD Stephen Donnelly will also serve.
The quorum for the committee will be five, including at least one member from the Seanad.
This means that at least five members will have to be present for the duration of all meetings of the committee.