Galway Senator Margaret Cox has resigned from the Fianna Fáil parliamentary party in protest at what she says is an imbalance in Government spending in the western region.
Last week, Senator Cox attempted to vote against the Finance Bill but was unable to do so due to a technicality.
While Ms Cox has resigned from the parliamentary party, she has not resigned from the party itself.
The Galway representative submitted her letter of resignation to the Taoiseach this afternoon. It is understood Ms Cox raised issues regarding the treatment of the West in the letter.
A Fianna Fáil spokeswoman confirmed receipt of the letter and said the issues outlined by her in the letter "have been and continue to be high priority for Fianna Fáil and the Government.'
Citing a contract signed today for the Galway to Ballinasloe road and the commencement of a mobile Breastcheck unit in Galway this month ahead of a static unit in September, the Fianna Fáil spokeswoman said there was "no question" that the issues raised were not being addressed.
In a statement tonight, Fianna Fáil said it was "surprised" by Senator Cox's decision. "It was Fianna Fail in Government which actually created the BMW region so that it could continue to receive priority funding," the statement said. "The facts show that the BMW region has actually seen a higher rate of employment growth in recent years than Dublin."
"In Galway West Fianna Fáil has a very strong ticket which combines two experienced and respected Ministers and a dynamic young candidate who has, in only a short period, shown the people of Galway City in particular that we are focused on a positive agenda for the future of Galway and Ireland as a whole."
During the debate on the Finance Bill last week, Senator Cox claimed the GDP per capita for Dublin was 33 per cent above the Irish average, while the corresponding figure for the BMW region was 25 per cent below average.
She also described the water crisis in Galway as a national emergency and an example of the Government's indifference to problems outside the Pale.