What on earth was Maurice Williamson thinking?
The National MP yesterday resigned as a minister following revelations he contacted a top-ranking police officer after a wealthy businessman with close ties to him was arrested on domestic violence charges.
The prime minister's office is understood to have questioned Mr Williamson over his involvement with Donghua Liu's criminal case.
In a statement Prime Minister John Key says he accepts Mr Williamson's resignation and describes the MP's actions as "a significant error of judgment".
It is hard to overstate the importance of independent police investigations in a democratic society.
Mr Williamson's actions could have brought that independence into question and that is cause for alarm.
For his part Mr Williamson said he was not trying to interfere in the police process and that he had made that clear to the police.
However, contacting a high-ranking police officer about an active investigation is a clear departure from what we expect from a politician.
Other ministers have suffered the same fate for similar errors of judgment. Surely these politicians should know better.
Mr Key had no choice but to accept Mr Williamson's resignation.
The prime minister has annoucned Tauranga MP and Cabinet minister Simon Bridges will take on the the Customs and Statistics portfolio until a new minister is appointed next week.
Mr Bridges already has the hot political portfolio of Energy and Resources which has made him a target for anti-mining groups.
The latest appointment, albeit an interim position, shows Mr Key's faith in his ability.