Conservative Party chairman Brian Dobbs has resigned, effective immediately.
In a statement, Mr Dobbs cites recent revelations and the events of the past week as his reasons for quitting, saying his position is now untenable.
He said 140,000 people voted for the party last election and he has taken the move with great sadness, knowing there is a strong conservative moment in New Zealand that needs representation and a voice in parliament.
Mr Dobbs has also resigned as a member of the Conservative Party.
Series of resignations
Colin Craig, who led the party through the 2014 general election and donated millions for its election campaign, resigned as leader last Friday.
Mr Craig said his resignation would enable the board to consider the leadership and direction of the party.
He said some inappropriate conduct had occurred between him and his former press secretary Rachel MacGregor, who resigned suddenly just before last year's general election, but rejected any suggestion of sexual harassment.
Ms MacGregor has accused Mr Craig of "clear factual inaccuracies" but said she was unable to comment further due to a confidentiality agreement the pair had signed.
Since last Friday, several other members of the Conservative Party's leadership team have resigned, including now-former chief executive Christine Rankin.