A senior Queenstown police officer is facing a code of conduct inquiry after being caught driving a police car at 149km/h.

Sergeant Ian Collin, who prosecutes in the Queenstown and Alexandra district courts, was issued with an infringement notice and an instant 28-day suspension after being caught speeding in the Kawarau Gorge on April 28, said southern regional manager for prosecutions, Inspector Richard Bruce.

It was understood he was fined $630, and stood down from his job while an internal inquiry was pursued.

Mr Bruce declined to comment about the inquiry and said he did not know when it would be completed.

Mr Collin moved to Queenstown from Auckland.

He was the first prosecutor solely dedicated to the two courts, which had previously been served by rostered prosecutors from Dunedin and Invercargill, the Otago Daily Times reported.