The governments of Poland, Czech Republic, Estonia and Hungary have blocked EU plans to commit the bloc to net zero carbon emissions by 2050.
The four countries vetoed the proposal at a meeting of the European Council on 20 June.
Climate Action Network (CAN) Europe director Wendel Trio said: “It is hard to believe that these four governments, driven by the narrow interests of their polluting industries, succeeded in their opposition to a widely-supported and badly-needed increase of the EU’s climate ambition.
“Failure to set new, higher EU climate targets is irresponsible given the climate emergency we are facing.
“EU leaders need to urgently come back to the negotiating table at another Council meeting to circumvent the veto ahead of the UN Climate Action Summit in September.”
CAN Europe said the EU needs to reach net zero emissions by 2040 at the latest to keep temperature rise to safe levels and reduce emissions by 65% by 2030.