Labour's Environment Spokesman Eamon Gilmore has criticised the Government's consultation document on proposals to introduce a carbon tax.
He told the Oireachtas Joint Committee on the Environment that there is no mention of the impact that such a tax would have on greenhouse gas emissions.
Deputy Gilmore said that he suspects the Government assumes the tax will have minimal impact on the environment.
Fine Gael Senator James Bannon said the move was another attempt to introduce tax by the back door.
Fianna Fáil TD Denis Cregan told the committee the Department of the Environment and the Environmental Protection Agency should address the committee on the environmental impact of introducing a carbon tax.
The Committee is due to discuss the proposed carbon tax again on Thursday.