Fine Gael TD Denis Naughten has voted against the Government in a motion to reverse cuts at Roscommon Hospital.
The Roscommon TD is now likely to lose the party whip as a result.
His party and constituency colleague Frank Feighan voted with the Government on the controversial issue, despite intense pressure.
The Government won the vote.
Hundreds of people took part in a protest outside the Dáil this evening to demonstrate their anger at the decision to cut emergency services at Roscommon Hospital.