Upper House MP Jeremy Buckingham has quit the Greens and will run as what he describes as an independent "real green" in next year's New South Wales state election.

His resignation follows colleague Jenny Leong's call in Parliament last month for him to quit over sexual harassment allegations made by a former party staffer.

Mr Buckingham has denied the allegations and said an independent investigation found no wrongdoing.

Greens NSW co-convenor Rochelle Flood said the party welcomed Mr Buckingham's decision to "comply" with its request for him to stand aside.

But in a fiery press conference, Mr Buckingham described the Greens as a "toxic organisation" and a "basket case".

"The NSW Greens abandoned the important principles of justice and democracy, is dominated by an extreme left faction and has lost its focus on the environment," he said.

'Not afraid to go rogue'

In announcing his intention to run as an independent, Mr Buckingham described himself as "the best environmental campaigner in NSW".

He said he had a strong track record on issues such as stopping coal seam gas, coal mines, championing renewable energy and backing healthy rivers.

"Voters know that I challenge conventions and I'm not afraid to go rogue," he said.

NSW Greens MP Cate Faehrmann said Mr Buckingham should never have had to resign.

"I share many members' concerns at how he has been treated," she said.