Local authorities have sought specific financing for the programme, which is a mandatory element of each council's Climate Action Plan, for years, but a dearth of money means they have had limited impact.
Under the government's Climate Action Plan 2019, councils were mandated to select an area of their county where methods to reduce carbon emissions are trialled, known as a Decarbonising Zone.
These include energy efficiency, biodiversity and other low-carbon initiatives which, if successful, could be rolled out on a wider scale.
Designated zones include the Aran Islands in Galway, the Dingle Peninsula in Kerry, and Ballymun and Ringsend/Poolbeg in Dublin.
However, Dublin's Regional Climate Action Coordinator, Sabrina Dekker, said measures within DZs are progressing at a glacial pace due to the lack of dedicated funding.
"There is no money is the thing," she said. "There's no funding committed by government to help us deliver. The ambition of the DZs is kind of stuck, because there's no money."
The Department of Environment points to existing government funding streams and EU grants to progress measures in DZs, but these pots of money are not dedicated to the initiative, so they merely spread existing funds thinner.
"They're making the argument that the money's out there, but that's money that they would have been able to access without having a DZ. It's not giving a priority to the area," Ms Dekker said. "The DZs are a nice idea on paper, but they do need funding."
She said if the government wants to see delivery of climate objectives through local authorities, they need to provide specific funding and heavily involve communities in the decision-making process around how it is spent.
"It's in the government's national Climate Action Plan, so it is a government ask of the local authority," she said, noting that more work should come with more money.
Local authorities have been lobbying government extensively to get dedicated funds for their DZs, but so far to no avail.
"So, the project was announced, then handed to local authorities without any funding mechanisms in place," said Darby Mullen, Dublin City Council Senior Executive Engineer at a climate action meeting in September.
"I've said to [the government], if we don't get funding and this falls, it'll be on the local authorities and not back on the department ... There was never any government funding made available through the project."
Other local authorities confirmed that they have received no dedicated funding for their DZs either.
A spokesperson for the Department of the Environment said there was a "wide range" of government funding programmes which deliver measures in DZs, citing the Community Climate Action Programme, Town Centre First scheme, Sustainable Energy Communities under the SEAI and active travel funding.
EU grants such as ELENA energy efficiency funding are also available, they said.
They also pointed to the funding of two climate posts in each local authority to oversee the implementation of climate action plans, and €11.7m for four Climate Action Regional Offices (CAROs) around the country.
In total, the department funded measures in local authorities' Climate Action Plans to the tune of just over €5.5m last year, up from €4.7m in 2023 and €3.3m in 2022.