Outspoken NSW Liberals MP Matthew Mason-Cox has been punished for his decision to cross the floor of Parliament and has been stripped of his position as chairman of a powerful committee.

Mr Mason-Cox was last week sacked as chairman of the upper house privileges committee, a position that attracts about an extra $20,000 a year. It is understood he will also be removed as deputy chairman of the newly formed public accountability committee.

Matthew Mason-Cox has been stripped of his position as chairman of a powerful committee. Credit:Daniel Munoz

Mr Mason-Cox embarrassed his Liberal Party colleagues in April when he refused to vote with the government and took the unprecedented step of crossing the floor.

His actions allowed the Greens to successfully move a motion forcing the government to be compelled to release the full business case for the relocation of the Powerhouse Museum.