Labour MEP Nessa Childers has resigned from the parliamentary party.
She has announced that she could no longer support a Government that was hurting the public.
"My dissatisfaction with the party in government has been known for some time; however recent statements from the Labour ministers have dismayed me," she said.
"They continue to insist that because of the dire economic situation there is no alternative to current government policies."
Ms Childers, who represents the Ireland East constituency, was elected to the European Parliament in 2009. She was previously a councillor in the Blackrock area of South Dublin from 2004 to 2008.
"I entered politics to help people and am now resigning from the Parliamentary Labour Party because I no longer want to support a government that is actually hurting people," she said in a statement.
Ms Childers will remain in the Labour Party, but will join fellow members in opposition to campaign for Labour policies.
Irish Labour MEPs are members of the parliamentary party, which also includes Labour TDs and senators.
The group meets once a week to discuss party policy in the Dail and the Seanad.
"It is predicted that Ireland will have to experience tight budgets for the foreseeable future, long after we exit the bailout programme," Ms Childers said. "My question is, will this government continue with business as usual and ignore the lack of fairness across government policy?"