The Left has levelled a "furious attack" on Michael Moore after the filmmaker released a documentary on Youtube castigating "the green energy scam", according to Sky News host Andrew Bolt.

Mr Moore released the documentary “Planet of the Humans,” free to charge this week to mark Earth Day.

The documentary casts doubt over the efficacy of renewables, in particular solar and wind energy.

The documentary filmmakers argue some green energy is hindering, rather than helping, the fight against dangerous climate change.

Mr Bolt said he did not agree with some of the documentary's content, but the filmmakers "do make some great points."

"This is why their film has come as a shock to so many," Mr Bolt said.

"Green groups are actually trying to get 'Planet of the Humans' banned.

"Isn't that a sign of the times? If you don't like the message, just try and ban it."

Image: AP