The Green Party under Catherine Martin would be committed to "the Green way, or the highway", the deputy leader has told members.
Ms Martin was speaking at the Green Party's hustings for the Midlands-North West and Northern Ireland constituencies in the party's leadership race. The race is pitting Ms Martin against current leader, Transport Minister Eamon Ryan.
Ms Martin said that if elected leader, she would commit to ongoing reviews of the programme for government and its implementation of Green policies.
"We are in government to implement Green policy, there is no other reason for us to be there. The leadership of the Green Party must be committed to the Green way or the highway, and I don't say that lightly, nor do I say it as a threat. But rather as a promise. That is my promise to our members. Each day, I will demonstrate the same green hands-on focus, the ambition, and the appetite, that I brought to the recent call for government talks, as the party's lead negotiator."
Ms Martin said that the party must now "kick on" and "not settle with being the fourth largest party in the Dáil". She said that the party must "capture people's hearts".
Mr Ryan said that the party must convince the public that a climate transition will not just be good for the environment.
"We have delivered a change in the way that the political system views climate change. We have to convince our people that this is actually going to be good for our country. That this is what we want to do, this is what's going to make our lives better and allow us to stand proud in terms of facing this incredible challenge. I think the work I've done in the last 10 years in climate gatherings where we really thought creatively about how you communicate this story I can put to good use as leader the Green Party for the next few years."
Mr Ryan said that a government land use plan was "key".
Asked by a member how the party will deal with allegations of bullying from here on, Mr Ryan said that the party had outgrown its current structures and must address its internal processes.
Ballots for the vote are being sent out this week, with a result due to be announced next Thursday.