AGL Energy – the country’s biggest carbon emitter – has won a stellar environmental, social and governance rating from a powerful institutional investor adviser two years after it was ripped apart partly because of its performance on climate change.

The high score from CGI Glass Lewis comes despite AGL – which operates the Bayswater and Loy Yang A coal power stations in NSW and Victoria – remaining on the watch list of environmental groups such as Climate Action 100+ over its carbon emissions.