The only remaining MEP for Fianna Fáil has announced he is changing his group in the European Parliament.
Brian Crowley is to leave the ALDE group and join the ECR - European Conservatives and Reformists Group.
The Eurosceptic group was set up by British Conservatives under David Cameron five years ago.
Crowley (left) and Michael Martin (right) at the Fianna Fail Ard Fheis in March
The move is a blow to Fianna Fáil leader Micheal Martin, who is understood to be deeply unhappy with the move.
Crowley's status within Fianna Fáil is now unclear as Fianna Fáil itself is still a full member of ALDE.
In a statement today, Brian Crowley said "I have decided to leave the ALDE Group in the EU to join the ECR Group, which will allow me to provide a better service for my constituents. The ECR Group is a non-federalist, pro-EU group who believes in giving a much stronger say to national governments rather than to EU Institutions".
"I also made this move to protect some jobs of Irish staff in Brussels, and not for any personal gain for myself, except my new group will allow me work more effectively for my constituents in Ireland South" he added.
