Safety concerns, rising costs and technological setbacks including delays to EPR projects in France and Finland have slowed nuclear projects since the Fukushima-Daiichi disaster in Japan in March 2011, he said.
At the same time, despite governments setting ambitious targets to cut greenhouse gas emissions responsible for global warming, emissions hit a record high in 2018.
Mr Birol said governments need to change their policies and consider new nuclear capacity and lifetime operating extensions for existing nuclear plants.
He said nuclear's contribution to Europe’s energy mix could fall to just 4% within two decades from 25% currently with huge consequences for both emissions and economies.
At the same time, the share of polluting fossil fuels in the global energy mix remains at about 63%, the same level as in the 1990s, he said.
Provisional data released by the agency last week showed that nuclear’s share of gross electricity production in the Organisation for Economic Cooperation and Development (OECD) in 2018 saw a modest increase of 1.1% to 17.7%.