Clare Bailey, leader of the Green Party in Northern Ireland, has rejected the draft programme for government in the Republic of Ireland.
The deal would see the Greens go into government alongside Fine Gael and Fianna Fail.
It was agreed last week, but has been opposed by a number of high-profile party members including three Green TDs.
Stormont MLA Ms Bailey originally abstained when the party’s parliamentary team voted on the blueprint but has now signed a statement alongside seven others saying a “a better deal is possible”.
It says: "As Green Party elected representatives and members from across this island, we believe that this draft programme for government represents an unjust recovery.
"That's why we will vote no on this draft Programme for Government.”
The Green TDs who are opposed to the deal are Francis Duffy, Patrick Costello and Neasa Hourigan, while other signatories of the statement include councillors Hazel Chu and Lorna Brogue and 2020 general election candidates Sean McCabe and Saoirse McHugh.
It goes on: "This offer of government represents one of the most fiscally conservative arrangements in a generation.
“Regressive taxation in the form of carbon and sugar taxes are included while corporation tax and the top rate of income tax remain unchanged.
"It's a deal that was negotiated in good faith but fails to deliver on our promise to tackle homelessness and provide better healthcare.
“It sets out an inadequate and vague pathway towards climate action.
"A better deal is possible - voting no on this Programme for Government is a step towards securing that better deal.
"Transformative change was called for by the electorate earlier this year. That call must be answered by not only the Green Party, but every party that promised positive change."
The Green Party has the highest threshold of the three parties to secure the approval of its membership.
Two-thirds of members registered to vote on the proposals ahead of next Friday must back the deal.
Just 195 of the Greens' 800 members north of the border have registered to vote on the draft programme for government.