The Green Party has said the Donegal South West by-election should be held immediately and remaining by-elections in the spring.
The matter will be communicated to Fianna Fáil at a Cabinet meeting this evening.
The junior coalition party made the decision after a High Court ruling earlier today.
The Court ruled there has been an unreasonable delay in holding the election. It is now 17 months since the seat was vacated by the election of Pat 'The Cope' Gallagher to the European Parliament.
"We've come to the conclusion that our position as a party should be that the impact of the High Court decision should be followed through in its spirit and the by-election Donegal South West should be held immediately at the soonest opportunity to move the writ," said Green Party Chairman Dan Boyle.
Sinn Féin, which mounted the challenge, is to move the writ for the by-election in the Dáil tomorrow morning.
Sinn Féin Senator Pearse Doherty welcomed the statement of support for an immediate by-election in Donegal South West from the Green Party but called on them to back up their words with votes in the Dáil tomorrow.