A police officer who avoided a drink-driving blood test because of a legal loophole has been charged with perverting the course of justice.

The Herald revealed in March that Constable Matt Hooper was pulled over by a patrol while driving in downtown Auckland about 11pm last December.

The off-duty Hooper did not identify himself as a police officer when breath-tested, and was taken back to the station where officers planned to obtain an evidential blood sample.

But Hooper allegedly asked if he could go to the toilet and emerged with a injury and was taken to hospital.

A Land Transport Act technicality states that blood collected in a hospital for alcohol testing can be used in a court only if the suspect has been hospitalised because of a car accident.

No drink-driving charges were laid against Hooper because of the technicality but he was stood down on full pay during the criminal investigation.

He returned to work on restricted duties in January and was the subject of an internal code of conduct inquiry.

Now Hooper, 29, has been charged with perverting the course of justice and will appear in the Auckland District Court at the end of the month.

Police spokeswoman Noreen Hegarty said Hooper was suspended from duties on full pay in April.

The Independent Police Conduct Authority is also investigating . The suspected drink-driving occurred two days before the police national prosecutions manager Superintendent Graham Thomas refused a breath test in Wellington, as revealed by the Weekend Herald in March.

Mr Thomas drove home after spending time at the police bar. He was followed by a volunteer community patrol team, which alerted police to a suspected drink-driver. An officer knocked on Mr Thomas' door and asked him to take the breath test. It is understood Mr Thomas said he had been drinking at home.

After refusing to take the breath test, as he is entitled to, Mr Thomas was spoken to by officials at police national headquarters. The internal inquiry cleared him of any criminal behaviour. He later lost his job but kept his rank, six-figure salary and car.