The EU says the deal shows it has the ambition to fight climate change, however environmentalists claim heavy industry has been granted too many exemptions.
Agreeing to reduce emissions by a fifth, in just over a decade, is seen as a major commitment by the EU on tackling climate change.
Nine east European states, who are heavily reliant on highly polluting coal-fired power sectors, have secured significant concessions.
Industrialised countries like Germany and Italy have also been pressing hard to protect their steel, chemical and ceramic industries.
The World Wildlife Fund asserted: 'This is a flagship EU policy with no captain, a mutinous crew and several gaping holes in it.'
However Environment Minister John Gormley, told a UN climate change summit in Poland today that the deal was realistic, achievable, and essential.
He added last year's dire predictions by the UN's advisory panel, the IPCC, were out of date and the opportunity to prevent dangerous impacts was closing quickly.
