Police bosses deny there are top-level documents describing a serious drink-driving allegation against a senior officer, first revealed by the Herald on Sunday in December.

Former national prosecutions manager Superintendent Graham Thomas is on extended leave from police headquarters after an incident early last December 13. Thomas refused to comment yesterday about allegations he drove drunk and then refused an evidential breath test.

Police headquarters have stated that there was no written documentation relating to the incident between key people including Thomas.

According to witness reports taken at the Johnsonville police station later that morning, Thomas admitted drinking when he was found asleep in his car by a neighbourhood patrol.

At that stage, the patrol did not realise Thomas was a police officer.

A community patrol report given to the Johnsonville police intelligence section and read to the Herald on Sunday states: "He [Thomas] said he was sleeping off after drinking. He said he was fine. At that point the community patrol officers ascertained he had been drinking.

"He was parked outside the Johnsonville Mobil service station. Community patrol officers saw the car again at the Johnsonville roundabout and they followed the car to his destination.

"They then followed the vehicle to his house ... Comms [Police communications centre] were called before that. Comms had asked the community patrol officers to stay with him."

When the superintendent arrived home, the patrol notified police of his address and an officer was dispatched to carry out a breath test.

After a 20-minute delay - the officer initially went to the wrong address - the officer knocked on the door and asked to carry out a breath test. He was refused.

According to the report, community patrol officers told the police communications centre the alleged offender was a "white male" with "glasses", "wearing a white T-shirt, dark trousers" and aged "between 40 and 50".

Community patrol officers gave witness reports to officers at Johnsonville Police Station until 1.44am. The Herald on Sunday understands those witnesses have not been contacted since.

Police would not answer further specific questions, including whether people at the bar Thomas was allegedly drinking at before the incident were interviewed.

The Herald on Sunday asked police under the Official Information Act for written correspondence to Police minister Judith Collins, Police Commissioner Howard Broad and to Thomas about the incident. Collins' office has confirmed the minister was briefed at the time.

In his written response to the OIA request, police national human resources manager Wayne Annan said specific information about the incident requested by the Herald on Sunday would not be provided because it "does not exist".

In a subsequent phone conversation, Annan said: "The request made was all written communication - there hasn't been any.

"Let me say something, an employee of police was asked by police to agree to undertake a breath test at his home.

"He declined. As he was entitled to do. This meant it is complete from an investigation perspective.

"Employment matters have now been concluded. The employee has been on a period of annual leave and sick leave.

"The employee has undertaken a period of medical rehabilitation for a minimum period of six months in an alternative position to his normal role."

Jon Neilson said in a later phone conversation that police wouldn't answer questions because the issue was a confidential employment matter.

A spokesman for Police Minister Judith Collins said yesterday it was not appropriate for her to comment on a police employment matter but opposition law and order spokesman Clayton Cosgrove called for transparency.

"It is a bit rich for Ms Collins to hide behind an employment issue. Ms Collins really should be asking the [Police] Commissioner to make available the results of the internal inquiry and provide the New Zealand public with an assurance that everybody is treated the same way and that the proper process followed looking into this matter."

Two of the country's top lawyers, Peter Williams QC and Nigel Hampton QC, said they believed there must be some documentation relating to the incident.

"I'm sure once they knew who it was, there would have been communications with people higher up the senior chain," Hampton said.

"There would have been a collection of information for possible criminal investigation and, or disciplinary prosecution, and, or employment issues.

Hampton said the case "has that feel" that police are looking after their own.

Employment specialists Fred Adelhelm, Auckland University of Technology professor Erling Rasmussen and Simpson Grierson partner Phillipa Muir all said it was "standard practice" to have written documentation in employment investigations.

Drink driving lawyer Chris Reid said the matter was an example of a "huge double standard".

"The police themselves expect people like you and me to comply when they come and knock on your door saying, 'We've had reports that you've been drinking and driving. We'd like to test your breath, please'.