Former Green Party councillor Peter Kavanagh said it had been a "very difficult decision" to announce his resignation from the party.
I've taken the very difficult decision to step down as Urlabhraí na Gaeilge & Gnóthaí Gaeltachta and resign from the Green Party/Comhaontas Glas with immediate effect.
— Cllr. Peter Kavanagh (@TheKavOfficial) January 25, 2021
I have never made my opposition to the Programme for Government a secret, having spoken against it... 1/2
Speaking to RTÉ's Drivetime, he said that it was a "culmination of a cultural shift within the party that has left me feeling isolated, I have basically run out of road".
He said: "At the moment any question or criticism of Government decisions is portrayed quite wilfully as disloyalty rather than the well-meaning dissent it is supposed to be.
"For example, I was quite critical, internally and publically, of the decision to partially reopen schools for Leaving Cert students with only three days' notice to rearrange the timetable and without consulting the teaching unions.
"When I voiced this opinion, I was called out for spreading misinformation about the safety of schools and I feel that is not conducive to a collegiate atmosphere in a small party of Government."
The councillor for Clondalkin in Dublin continued: "I worry that the Greens are struggling to put their stamp on the Government. I believe the party has fundamentally changed in the past year.
"When I joined five years ago, one of the things that attracted me was its membership-led ethos and we saw that last year when we had a special convention online that allowed everybody to have their say on going into Government."
Cllr Kavanagh said he opposed the move to go into coalition with Fianna Fáil and Fine Gael but 74% agreed.
He said: "I did not think it was a good deal but I went along and tried to support my colleagues. But I can't be uncritical. I worry for the survival of the party."
He said there are certain senior members of the party who are "driving the agenda, we see that in the debate over CETA [Canadian European Trade Agreement]."
Cllr Kavanagh said he did not know how much disquiet there was in the party but he expected resignations.
He added: "If the party does not get its act together and start dealing with things that I have raised we certainly will see resignations from people who are unhappy about compromises in the programme for Government."
