NSW Greens MP Cate Faehrmann has issued a blistering attack on her party, saying she is "beyond appalled" with many members and fears the Greens have been "infiltrated by extreme left forces".

Ms Faehrmann, a former chief of staff to Greens' federal leader Richard Di Natale, said the party's decision to force fellow MP Jeremy Buckingham to resign was a new low for the NSW Greens.

Greens MP Cate Faehrmann says her party is at a crossroads. Credit:Louie Douvis

Her comments will further inflame tensions in the divided party as it prepares for the state election.

The NSW Greens voted on Saturday to kick Mr Buckingham off the party's 2019 election ticket, amid accusations made under parliamentary privilege that he had committed an act of "sexual violence" against a former Greens employee.