Key Points:

A top police officer has been stood down after refusing to take a drink-driving breath test.

Superintendent Graham Thomas has been removed as the head of the national prosecutions service in Wellington following an internal police investigation into an incident in December.

The former acting Auckland area commander has been on leave since he was asked to take a breath-alcohol test after driving home from a police bar.

Police spokesman Jon Neilson said Mr Thomas declined the breath test "as he was entitled to do", but refused to answer further questions, citing employer confidentiality.

But the Weekend Herald understands Mr Thomas drove home after spending time at the police bar in Wellington.

He was followed home by a volunteer community patrol team, which alerted police to a suspected drink-driver.

A sergeant knocked on Mr Thomas' front door and asked him to take the breath test. It is understood Mr Thomas told the officer he had been drinking at home.

After refusing to take the breath test, Mr Thomas was spoken to by officials at police national headquarters.

The internal inquiry is now complete.

Mr Thomas has been on annual and sick leave since mid-December - on a six-figure salary - and Mr Neilson said "employment matters" had also been completed.

"The employee is undertaking a period of medical rehabilitation for a minimum period of six months in an alternative position to his normal role," he said.

It is not an offence to refuse an initial breath-screening test. But a police officer can then require someone to take an evidential breath test. Refusing to take the second breath test is an offence.

Police Minister Judith Collins said she was aware of the incident, but declined to comment further as it was an internal employment matter.

This is not the first time a senior police officer has been in the limelight over alcohol breath-tests.

In 2000, the then Police Commissioner Peter Doone resigned from his $275,000-a-year post after two top-level reports criticised his conduct on election night in 1999.

Mr Doone spoke to a junior constable who stopped a car driven by his partner, Robyn Johnstone. Deputy Commissioner Rob Robinson, who investigated the incident, said Mr Doone's actions were inappropriate.

The State Services Commission recently cleared Police Commissioner Howard Broad after claims he avoided a police breath-test checkpoint 16 years ago.

In 1992, Mr Broad was stopped by a Ministry of Transport traffic patrol in Christchurch. He acknowledged having a couple of drinks with a meal, so the officer asked him to park the vehicle and to stop driving. But Mr Broad was not breath-tested.

Superintendent Thomas made headlines five years ago, when it was revealed that he made the decision to prosecute National MP Shane Ardern for a protest in which he drove a tractor up the front steps of Parliament.

The police were later criticised by Judge Ian Mill for wasting court time, and the charges were withdrawn.