Government inaction has been blamed for the first increase in carbon emissions for four years.
On the day that the Kyoto Agreement on reducing greenhouse gases is commemorated, Opposition parties said Government dithering had led to carbon dioxide emissions increasing by more than 1.3 million tonnes in 2005.
The Environmental Protection Agency (EPA) confirmed a 1.9 per cent increase to just under 70 million tonnes - putting Ireland 12.4 per cent behind its Kyoto target of a 13 per cent increase on 1990 levels between 2008 and 2012.
Ireland will be forced to purchase carbon credits under the EU's emissions trading scheme to make up for the overshoot, and 270 million has already been set aside for this.
Fine Gael environment spokesman Fergus O'Dowd said the taxpayer is paying for the "absence of ideas and lack of drive".
EPA director-general Dr Mary Kelly said the increase in transport emissions was "particularly worrying" as it has been increasing steadily at a rate around 7 per cent since 2003.
Inadequate public transport provision, increased vehicle ownership and a surge in the sale of larger, less fuel-efficient vehicles has been blamed for the increase and the trend continued last year.
Mr O'Dowd said that a Fine Gael-led government would bring in a higher vehicle registration tax for "gas guzzlers," a requirement that all petrol and diesel be blended with biofuels, and investment in public transport.
"When it comes to CO2 discharges from vehicles, a carrot-and-stick approach is needed to either get people off the road or, if they stay on the road, to do so in a way that pollutes far less," he said.
Minister for Natural Resources Noel Dempsey this week announced that all vehicle fuels would have to contain 5.75 per cent biofuel by 2009 and 10 per cent by 2020 in line with EU directives.
Labour party environment spokesman Eamonn Gilmore said the latest figures were a damning indictment of the Government's record.
He called for immediate publication of the Government's delayed review of the National Climate Change Strategy.
"It was to been published by the end of 2006, but there's still no sign of it. This attitude echoes the hold-up in putting the strategy together in the first place, which was delayed by three years," Mr Gilmore said.
The EPA report says agriculture remains the largest contributor to Ireland's emissions but this has been steadily declining.
A 2.4 per cent increase in power generation was due to two peat burning generators coming into operation.
There was a small increase in industrial emissions while domestic output - largely home heating - remained virtually unchanged.
The Green Party's transport spokesman Eamon Ryan that in light of the findings the Transport 21 strategy should be reviewed with an increased focus on public transport.
"On the second anniversary that our Kyoto commitments began, I am calling on all political parties to commit to changing the Transport 21 Plan, should they be returned in the next Government," said Mr Ryan.
The EPA figures are provisional until March this year when they will be submitted to the European Commission.