A leading think tank and lobby group on climate change is fighting for its survival after the multimillion-dollar support of its primary benefactor ran out.

The Climate Institute, which has become one of Australia's most prominent environment and climate groups since being set up through a bequest in 2005, suffered a 62 per cent fall in revenue last financial year.

Climate Institute chief executive John Connor. Credit:Brendan Esposito

It came at the end of a decade of backing from foundations run by Rupert Murdoch's niece Eve Kantor and her husband, farmer Mark Wootton, who created the institute with a goal of helping set Australia on a path to combating climate change.

Their commitment was originally planned for five years through the Poola Foundation, set up from the estate of Ms Kantor's late brother Tom. It was extended to 10 years when the first round lapsed during the then brutal political debate over climate change in 2010, but was never intended to continue beyond that.