Mining giant Rio Tinto has reported NSW Greens MP Jeremy Buckingham to police, alleging he trespassed on its Mount Thorley Warkworth open-cut coal mine to film a video.

Two NSW Police detectives questioned Mr Buckingham and staffer Max Phillips at NSW parliament house on Thursday after he uploaded a video of the controversial mine on social media on August 17.

Mr Phillips said police travelled from Singleton after a representative from Rio Tinto made a complaint about an alleged trespassing.

He said the officer had warned that the pair could be issued a criminal infringement notice.