THE Greens leader, Senator Christine Milne, has endorsed a controversial hoax by an anti-coal activist, saying his actions were ''part of a long and proud history of civil disobedience, potentially breaking the law, to highlight something wrong''.

Her comments came after a tweet by her colleague Lee Rhiannon, who publicly congratulated Jonathan Moylan, an activist under scrutiny for impersonating a bank and temporarily wiping $314 million off the value of Whitehaven Coal.

"Companies that are driving climate change will increasingly come under scrutiny and be exposed for their investments" ... Senator Christine Milne, Greens leader. Credit:Alex Ellinghausen

''Congrats to Jonathan Moylan, Frontline Action on Coal, for exposing ANZ investment in coalmines,'' Ms Rhiannon tweeted on Tuesday night.

Mr Moylan orchestrated an elaborate hoax on Monday in which he tricked investors into thinking that a recent $1.2 billion loan arranged by ANZ for Whitehaven had been cancelled on ethical grounds.