The Green Party yesterday decided to end negotiations with Fine Gael concerning forming a new government.
The decision of both the Social Democrats and the Labour Party to opt out of negotiations weakened the case for the Green Party to join such a coalition.
The Greens would have felt more comfortable joining a coalition that was a true "rainbow" administration, sources said, and which would have included Labour and the Social Democrats – fellow centre-left parties. However, Green leader Eamon Ryan has said the party could still help with "the formation of a viable government", but that is likely to be from the opposition benches.
It is understood the Greens also felt that the ideas put forward by Fine Gael were not radical enough, with particular concern over the housing paper tabled this week.
Mr Ryan also said the Dáil numbers mean that Fine Gael and Fianna Fáil have to work together, and make a minority administration extremely difficult to assemble.