A move by the National Party to seek leave for a vote of no confidence in parliament's speaker Margaret Wilson has been blocked by Labour.
National claims Wilson exercised her discretion in a "narrow and legalistic" manner by refusing to send a report on the Labour MP Taito Philip Field to the Privileges Committee.
The role of parliamentary speaker is the third highest office after the governor general and the prime minister.
Wilson is a Labour MP but in the role of speaker is expected to be impartial and act as parliament's referee.
But her refusal to send allegations of corruption by Field to the committee has sparked a rare challenge to her authority.
On Wednesday, Wilson ruled there was no evidence Field used parliamentary processes to advance the immigration cases at the centre of the report, so no question of privilege arose.
National's deputy leader Gerry Brownlee says the party is astonished at the ruling and he says the government is now complicit in Field's actions.
Meanwhile, the National Party says the Department of Labour has a duty to investigate Field for breaches of the Minimum Wage Act.
National has lodged an official complaint because it believes the MP for Mangere substantially underpaid Thai immigrants he was assisting with immigration matters. It says the Department of Labour should interview Field and the Thai workers he employed to work on houses he owned.
It also says invoices and GST receipts should be examined to determine whether employment law was breached. The party has written to the Department of Labour asking it to examine whether the Labour MP breached the Minimum Wage Act. Secretary of Labour James Buwalda says he cannot comment on the letter but says the department would give it proper consideration.
The Green Party says two decisions in the case do nothing to restore public confidence in parliament. Co-leader Jeanette Fitzsimons says the speaker's ruling that there was no evidence Field used parliamentary processes to advance the immigration cases and an earlier ruling that cleared Field of a conflict of interest will only fuel public scepticism about parliament policing its own standards.
Fitzsimons says parliament must make it clear that such behaviour is not considered acceptable - perhaps by developing a code of conduct for members.
Attacks on the speaker's character are among the most serious an MP can make because they are seen as an attack on the institution of parliament itself.
National does not have the numbers to unseat Margaret Wilson but
the move is symbolic - it has been two decades since such a
challenge has been made against a speaker - a powerful signal that
National is not letting the Phillip Field issue die.