"The drive to clean up the world's energy system has stalled," IEA Executive Director Maria van der Hoeven said in Paris, where the agency has headquarters.
A report from Pew Charitable Trusts this week said that, among members of the Group of 20 industrialized economies and the European Union, only China posted a net increase in attracting investors to its renewable energy sector when compared to 2011 figures.
The IEA said carbon intensity per unit of energy produced was around 2.39 tons of carbon dioxide per ton of oil equivalent in 1990. It took 20 years for that level to drop to 2.37 tons of carbon dioxide.
"Despite much talk by world leaders, and despite a boom in renewable energy over the last decade, the average unit of energy produced today is basically as dirty as it was 20 years ago," van der Hoeven said in a statement.
She added the figures should serve as "a wake-up call" to the international community concerned about the effects of greenhouse gas emissions and warmer temperature trends.