The two Green Ministers "have each clocked up more mileage per month than the Taoiseach", Labour communications spokeswoman Liz McManus has claimed.
During a pre-budget estimates debate, Ms McManus said she was "startled" to find in a reply to a parliamentary question on ministerial cars that Minister for the Environment John Gormley and Minister for Communications, Marine and Natural Resources Eamon Ryan had accumulated more driving miles than the Taoiseach.
Attacking the Green Party in Government, she said "there have been many photo opportunities of Green Ministers on their bikes. While I accept a Minister's job requires car travel, it again raises the difference between the reality and rhetoric of the Government."
Ms McManus's question revealed that Mr Gormley clocked 11,870km in his car since it was acquired in July this year, and Mr Ryan clocked 11,800km. The Taoiseach's car, acquired in April 2006, had clocked up 69,350km.
She said of the 18 ministerial cars "only five cars are hybrid petrol-electronic, and none are biofuel".
Both Green Party Ministers' cars are hybrid vehicles. Government chief whip Tom Kitt, Minister of State for Children Brendan Smith and Attorney General Paul Gallagher also use hybrid vehicles, the reply shows.
The petrol car used by the Minister for Finance was acquired in April 2004, and accumulated 140,950km, while 49,750km were clocked up by the Minister for Health in a petrol car acquired in December 2006.
The petrol vehicle used by the Minister for Transport and acquired in December 2003 has accumulated 235,840km.
Ms McManus said the low level of eco-friendly cars "questions the Government's commitment to dealing with its carbon footprint, and the wider issue of reducing energy consumption by example. A government with a green tinge should set a good example. Instead, there is a feeling of being let down, with no reassurance in the pre-budget outlook report."
The Wicklow TD renewed criticisms of Mr Ryan's renewable resources scheme, which she described as a "complete sham".
The Minister "was reduced to raiding his broadband and energy research fund to allocate moneys to the renewable grant scheme", for renewable technologies such as solar panels and heating systems.
She said money for broadband was being used "to stuff the hole left by Sustainable Energy Ireland when it ran up bills across a range of existing schemes, including the defunct Greener Homes scheme. In reality, there are no moneys for the new scheme announced by the Minister. It is a sham."
Mr Gormley said the published pre-budget estimate for his department "provides for €2.8 billion, comprising capital spending of €1.978 billion and current spending of €888 million".
He had "placed great emphasis on the achievement of the highest environmental standards through partnership with the local authorities and other agencies within my remit".