Two of Labour's sitting senators, Kathleen O'Meara and Derek McDowell, have decided against standing in the forthcoming Seanad elections.
Meanwhile, a third Labour senator, Michael McCarthy, has failed to secure a nomination from the party.
Labour's national executive council (NEC) decided on Saturday to nominate six first-time candidates to stand for the party in the Seanad election, all of whom are seen as having a chance of winning a Dáil seat for the party at the next election.
Because of the number of Labour councillors, the party has sufficient strength to return five of the candidates to the Seanad while a sixth success is possible subject to a voting pact or deal with another political party or grouping.
The candidates nominated by the party include barrister Alex White, who stood unsuccessfully for the Dáil in Dublin South, and who will be standing on the Cultural and Educational Panel.
Brendan Ryan, who stood in Dublin North, has been nominated to stand on the Administrative Panel, while the party's unsuccessful candidate in Meath East, Dominic Hannigan, will stand on the Industrial and Commercial Panel. Eric Byrne, who lost out for the final seat in Dublin South Central, and Phil Prendergast, who stood in Tipperary South, will both be candidates on the Labour panel.
Alan Kelly from Tipperary North, who will be standing on the Agricultural Panel, is the only candidate not to have stood for the party in the general election.
A former chairman of Labour Youth, he is now expected to replace Senator Kathleen O'Meara as the party's Dáil candidate in Tipperary North.
Yesterday Senator O'Meara said she had decided not to go forward for the Seanad following her failure to take a seat in Tipperary North on her third attempt.
"I am taking some time out, but I'm not retiring from politics," she said.
She added that while she was not taking it personally, she had to be realistic about the vote she secured at the election and her chance of ever taking a seat in Tipperary North.
Michael McCarthy, the youngest senator in the Oireachtas during the last term, failed to secure a nomination from the party.
He stood unsuccessfully in the three-seat constituency of Cork South West.
Breda Moynihan Cronin, who lost her seat in Kerry South, also decided against putting her name forward for the Seanad election.
However, she will continue in her position of chairwoman of the party.
A total of 25 people put their names forward to the party's NEC seeking Seanad nominations. Unsuccessful candidates included Arthur Spring, nephew of former Labour leader Dick Spring, and Cllr Aidan Culhane from Dublin South.