An Oireachtas committee has heard that Ireland will struggle to meet its national and EU obligations on climate, leading to "a significant call on the public purse".
The chairperson of the Climate Change Advisory Council said the "scale of the challenge" facing Irish society to address the climate crisis is "enormous".
Marie Donnelly told the Budget Oversight Committee that Ireland's response to date has been "disappointing".
In her opening statement, she said Ireland needs to be free of fossil fuels by the end of the next decade.
Ms Donnelly said by the EPA’s best case scenario estimates, Ireland’s emissions will only be 23% lower in 2030 than in 2018, despite a national target of a 51% reduction during the same period.
The chairperson said the cost of Ireland missing its EU climate and energy targets could be between €3 billion and €26bn.
She said it is vital that "we employ all the tools at our disposal to help achieve these targets".
"The tax system should support achievement of our climate targets and it can do this by pushing us to reduce our dependence on fossil fuels," she said.
Ms Donnelly said fossil fuels must be phased out by as early as 2029, with "limited to no opportunity for new investments in fossil fuel systems".
She added that Ireland’s tax system "supports our use of fossil fuels through environmentally harmful subsidies", including exemptions from fuel and excise taxes.
"This is inconsistent with Ireland’s climate objectives and should not be allowed to continue," she said.
She said the Government needs to give "clear signals on the direction of travel" for the carbon tax and other measures to support low carbon investments.
She also called for the removal of fossil fuel subsidies as it is "widely accepted that phasing them out will reduce emissions".
Ms Donnelly said the total budgetary cost of fossil fuel subsidies was €4.7bn in 2024.
She said the excise rate on petrol and diesel should be equalised as "given the impacts on both air quality and climate, there is no reason to favour diesel".
