A Fianna Fáil TD, speaking on RTÉ's Your Politics podcast, has said supporting Fine Gael's housing policy in the last government led to the party suffering in February's general election.
Jim O'Callaghan, the former justice spokesperson for Fianna Fáil, said he thinks part of the reason the party did not do as well as they wanted was because they were seen as "too close to Fine Gael".
He said: "I think the housing thing was a huge issue. I think we were perceived as condoning Fine Gael policy on housing and I think we suffered for that."
Fianna Fáil got 38 seats, far fewer than the 50 it was aiming for.
Mr O'Callaghan said there were periods during the confidence and supply arrangement where Fianna Fáil "stood up to Fine Gael where we were completely different".
But he said the polls in January ahead of the general election showed for the first time since the agreement began in 2016 that both parties were down in the polls, while Sinn Féin had grown.
The backbench TD said he had not fallen out with the Taoiseach over not getting a ministerial position and that he has a "very good relationship with Micheál Martin".
He told the podcast it was a difficult decision to refuse a junior role within the Ministry of Justice, but that he did so after assessing what he thought was a "limited role".
The former frontbencher said when Micheál Martin phoned him about the position, he told the Taoiseach it would have been preferable if Fianna Fáil held the Justice or Foreign Affairs portfolios. Both departments are now held by Fine Gael.
He said it is difficult for a leader to select a negotiating team and cabinet ministers and that he will now work to strengthen the party as it will be extremely important to protect Fianna Fáil's identity.
Asked about his party colleague Barry Cowen's driving offences, he said the penalty has been paid and the extra penalty paid is the exposure of ridicule and embarrassment and public humiliation.
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Mr O'Callaghan's comments came after Micheál Martin confirmed there would be a full review of Fianna Fáil's general election.
At last night's parliamentary party meeting, the Taoiseach set out a programme entitled "Strengthening our Party".
He told TDs that the party needs to understand and learn from February's general election so that Fianna Fáil is "match fit" for the next one.
The review will report later this year.