A leading unionist has attacked Air New Zealand chief executive Rob Fyfe over the company's "grubby deal" with police that has led to staff caught drink-driving being penalised twice.

Andrew Little, secretary of the Engineering, Printing & Manufacturing Union and also president of the Labour Party, said the police had circumvented privacy and information laws and the airline had co-operated.

But Air NZ last night dismissed his attack as "political grandstanding".

Last week, it emerged that a senior police officer had referred in internal communications to "an apparent drink-drive problem" at Air NZ and the need to address "what may be a culture which accepts alcohol consumption, prior to working".

Mr Fyfe retorted to the police in a letter he made public that the claims were unsubstantiated. He said the airline's policies had resulted in less of a drink-drive culture at Air NZ than in the population as a whole.

A Weekend Herald columnist praised Mr Fyfe's "aggressive defence".

But Mr Little said that "Mr Fyfe's response was less one of management heroism and more one of anger that the grubby deal had blown up in the airline's face".

He said that under that deal, airline staff processed for drink-driving faced criminal prosecution, appropriately, but also had the facts disclosed to Air NZ, so it could "exact a second punishment, usually dismissal, for the same offence".

Both sides knew they were sailing "close to the wind" legally, he said.

"After the EPMU challenged this practice through complaints to the Privacy Commissioner and the Independent Police Conduct Authority, the police - desperate to find some justification for their irregular actions - claimed a drinking culture at the airline."

And this had prompted Mr Fyfe's outburst, Mr Little said.

The union's privacy and police conduct complaints have yet to be determined.

The police have portrayed their release of drink-driving information to an employer as preventive action to protect public safety.

A December police memo said Auckland police had processed four Air NZ staff for drink-driving - a pilot, a flight attendant and two mechanics.

The flight attendant was on her way to work for an overseas flight. She was sacked, but has challenged the dismissal at the Employment Relations Authority, whose verdict is pending.

Air NZ has stated it has twice used the Official Information Act to obtain details about employees in safety-sensitive areas caught driving to work with excess blood-alcohol.

An airline spokesman, Mark Street, last night defended this, saying it was in line with the company's policy of zero blood-alcohol while at work.

"Safety of our passengers and staff is paramount," he said. "However, it would appear ... Andrew Little would prefer to disregard the interests of the travelling public in preference for political grandstanding."

Mr Street said the Employment Relations Authority was the proper judge of Air NZ's actions.