A Labour TD has said he cannot vote to support the sale of Aer Lingus in the Dáil this afternoon.
Michael McNamara's decision means he is set to be expelled from Labour's parliamentary party.
The Clare TD says Shannon Airport's current business level is no guarantee that services would not be cut in the future.
He also says the IAG takeover is a "gamble" which he is not prepared to support.
He said: "I'm not prepared to gamble with what I believe is key to the economic development of this state, all of this state.
"I don't have confidence in this guarantees at the moment as they stand.
"On that basis Minister (Donohoe), I regret that I will not be able to support you in this afternoon's motion."
Deputy McNamara's Labour Party colleague has dismissed his concerns over the sale of the airline, however.
Minister for Business & Employment Ged Nash says he has been given a number of assurances on jobs - with IAG promising there will be 635 net new positions if the proposed deal goes ahead.
Minister Nash insisted that this deal is in the best interest of the Shannon region.
“While I understand why he may have taken this decision, I don’t necessarily accept it,” he said.
“Michael himself has recognised that the airport at Shannon, and indeed the local Chambers of Commerce have welcomed this deal as being in the best interests of the region, in the best interests of jobs, and the best interests of securing the company’s future going forward.”