Fianna Fáil TD Jim O'Callaghan has turned down a junior ministry.
Mr O'Callaghan told the Irish Times that he had been offered a role in the Department of Justice, serving under Minister Helen McEntee.
Mr O'Callaghan would have had responsibility for law reform.
However, he turned down the offer from Taoiseach Micheál Martin, telling the paper that he believed his energies would be better used as a backbench TD.
Mr O'Callaghan said he would focus of strengthening the Fianna Fáil party.
"At a time when many of our party’s senior members will be preoccupied with their ministerial duties, I want to devote more time to strengthening our great party by making it a more attractive option for young voters.
"I also believe Fianna Fáil needs strong voices outside government who can ensure that our party’s identity can be protected during the term of this coalition government."
Mr O'Callaghan was not part of the party's negotiating team, but served as the party's justice spokesperson in the last Dáil.
The government will today announce 17 junior ministers.
Fine Gael's Joe McHugh, the former Education Minister, has also turned down a junior ministry in the new government.
Earlier today,reported that Fine Gael Kerry TD Brendan Griffin, the former junior tourism minister,
Mr Griffin was not given another junior role by Fine Gael leader and Tánaiste Leo Varadkar today as calls were being made to TDs about positions.
understands that, despite speculation Mr Griffin would get a position, he has lost out to other party hopefuls.