Taoiseach Micheal Martin has been accused of a "cop out" on commitments made at COP26 before "the ink is dry on the agreement".
At the climate conference in Glasgow this week, Ireland signed up to a global pledge to limit methane emissions by 30% compared with 2020 levels.
But the Government has indicated that the pledge will not be included in Ireland's forthcoming carbon budgets, which will target a 10% cut in methane, as well as larger reductions in other gas emissions.
Social Democrats co-leader Roisin Shortall questioned if the Government's actions on climate will meet its rhetoric.
Speaking during Leaders' Questions in the Dail, she said: "The omens are not good, it has to be said.
"Yesterday you said Ireland would sign a pledge to reduce methane emissions by 30%, before hastily adding that this was a global target and not a national one.
"We hear the climate action plan contains a target of just 10% reduction and the Tanaiste also used this 10% figure yesterday.
"Can you explain the purpose of publicly signing up to a 30% reduction target, when it seems you have no intention of even even attempting to achieve that?"
Ms Shortall said that if every country took that approach there would be "zero chance" the targets would be met.
"Why are you making commitments at Cop that you cop out of as soon as the ink is dry on the agreement?" she asked.
Sign our petition calling on COP26 leaders to tackle climate change head on below, or click here.
Responding, Mr Martin insisted the Cop26 agreement of a 30% reduction in methane is a global target, towards which individual countries will have to contribute.
He accused Ms Shortall of an "abundance of negativity".
He said: "You seem to persistently want to seek to undermine what are genuine and transformative decisions by this Government to step-change our response to climate change, which we have done through the climate action legislation, through the establishment of the climate council and the carbon budgeting that will occur.
"On the global methane pledge, I think the deputy is being somewhat disingenuous here.
"Read the pledge. Read what people have signed up to. It is a global pledge.
"So globally, collectively, in different ways and through different mechanisms, countries who sign up will contribute to that overall 30% global reduction in methane."
Mr Martin said the Government's climate action plan will "deal with every sector", including energy, transport, agriculture, land use and deforestation.
Ms Shortall also asked the Taoiseach for clarity on plans to cull the national herd as part of Ireland's climate goals.
She noted that the Green Party has called for a reduction in size, while members of the other coalition parties, Fianna Fail and Fine Gael, have "mysteriously started to use the phrase "stabilisation".
Mr Martin did not respond to the question despite repeated requests from Ms Shortall.
