Ireland will miss its targets to slash greenhouse emissions by 2020 with the Government's environmental and energy policies.
The Environmental Protection Agency (EPA) is forecasting that the Republic will only cut the release of harmful gases by 4% to 6% of 2005 levels while the target was 20%.
And t he watchdog said emissions are projected to increase to 2030 and beyond.
EPA director general Laura Burke said the forecasts are disappointing and Government policies to reduce emissions and meet compliance obligations are failing in an improving economy.
"In addition, Ireland has a national policy position that commits us to reducing our carbon emissions by at least 80 per cent compared to 1990 levels by 2050 across the electricity generation, built environment and transport sectors while achieving carbon neutrality in the agriculture and land use sectors," she said.
"If we are to realise this policy position and our aspirations to transition to a low carbon economy, then any new measures to be included in the upcoming and future National Mitigation plans need to be innovative and effective to get Ireland's emissions back on a sustainable trajectory.
"This will take planning, investment and time but can be achieved in the overall framework of national, EU and global commitments."
The EPA said the vast majority of Ireland's non-Emissions Trading Scheme gases in 2020 will be from agriculture at 45% and transport at 29%.
From 2015 to 2020, farming emissions are forecast to increase by 4% to 5% while transport emissions are projected to show strong growth over the same period of 10% to 12%.
The EPA warned that n ew obligations for Ireland to reduce greenhouse gas emissions from 2021 to 2030 are expected to be agreed by the European Union next year.
The further away Ireland is from the 20% reduction target in 2020, the more difficult the compliance challenges in the following decade are likely to become, it said.
Denis Naughten, Minister for Communications, Climate Action and Environment, said the report is a stark picture of the challenges facing Ireland.
"It is clear that there are no easy options to reduce our greenhouse gas emissions on the scale required in the coming decades," he said.
Mr Naughten said Ireland's first National Mitigation Plan, which will set out policies on decarbonisation and is currently undergoing public consultation, will be complex and often expensive to implement.
"However, in many cases, these options will have a range of environmental, economic and other benefits, not just in relation to reducing greenhouse gas emissions, but also in relation to a range of other environmental indicators and in developing a more sustainable economic framework for Ireland in the decades to come," the minister said.
Mr Naughten also said the lack of progress on emissions was in part due to the inability to invest in greener policies in the recession.
He said he would argue that the 2020 target was not consistent with what was achievable on an EU wide cost-effective basis.
"Though not unexpected, given the welcome return to economic growth in Ireland, it nevertheless serves to further reinforce the difficult decisions ahead of us as we try to further reduce our emissions out to 2030," he said.
Green Party leader Eamon Ryan said the failure to meet targets was a national embarrassment and that Ireland will be one of only two European Union states not to meet the 2020 requirements.
"The Government has seen emissions reduction as a cost rather than an economic opportunity for Ireland," he said.
"Transitioning to a Green economy is an economic opportunity that we are missing out on. Instead, the gulf between Government's empty rhetoric and the actual situation will cost us dearly in our quality of life."