The Fine Gael MEP, Mr Joe McCartin, has told the party he will not seek re-election to the European Parliament in the election next year.
Mr McCartin's decision to retire was expected. Aged 64, he has been an MEP for Connacht-Ulster constituency since 1979. The Fine Gael leader, Mr Enda Kenny, said his service was outstanding.
The former TD, Senator Jim Higgins, has indicated that he wishes to stand in the election.
It is thought another former TD, Mr Gerry Reynolds, might also seek to stand. Mr Reynolds resigned the party whip on Leitrim County Council in protest at the party's policy of opposing the use of Shannon airport before the Iraq war.
There are three European seats in Connacht-Ulster. However, this is likely to be reduced to two when the total number of Irish seats is reduced to 13 from 15 in a reorganisation of the parliament.
The reduction, which takes place in the context of the EU's expansion into the former Soviet bloc, is likely to increase competition for seats significantly.
The other two seats in the constituency are currently held by the Independent, Ms Dana Rosemary Scallon, and by Fianna Fáil's Seán Ó Neachtain. Mr Ó Neachtain replaced Mr Pat "the Cope" Gallagher when he was elected last year to the Dáil.
A convention to select the Fine Gael candidate is not expected until next year, after the Boundary Commission completes a review of all the Irish EU constituencies. Other candidates likely to stand in Connacht-Ulster included the Independent Sligo TD, Ms Marian Harkin, who is being courted by the PDs. Those in the race in Fianna Fáil are believed to include the Galway TDs Mr Frank Fahey and Mr Noel Treacy.
