A British sailor caught drink-driving in New Zealand - and then let off - claims she had had only three wines, and hit a parked car because her passenger grabbed the wheel.

Chief Petty Officer Lauren Cobby has denied reports she escaped conviction because she was a foreign visitor, saying the judge let her off because the consequence "exceeded what was deserved for the offence".

The 29-year-old was on exchange in New Zealand when she crashed on Onewa Rd on the North Shore - after a night at the Birkenhead RSA - and returned a breath-alcohol reading of 829mcg. The legal limit is 400mcg.

A Defence Force spokesman said its lawyers spoke to police about invoking the Visiting Forces Act, which allows courts to dismiss charges for overseas personnel, and the sailor was discharged without conviction in the North Shore District Court in June.

But, in a letter to the Herald, Chief Petty Officer Cobby said she was forced to drive that night and crashed because of a passenger.

After a booked dial-a-driver didn't turn up, no one could give her a phone number for the company and she couldn't get hold of her host, so she got behind the wheel.

"I felt there was no alternative as I didn't know where to go, I had only consumed three glasses of wine throughout the evening and thought I would be safe to drive."

A man, who she assumed was service or ex-service, asked for a lift.

"Whilst driving down the road, he reached over and grabbed the steering wheel, causing me to lose control and crash into the parked car."

Chief Petty Officer Cobby said the man was known to the police and had been in trouble before.

"Obviously I was unaware of this until afterwards."

She said the incident had been absolutely terrifying, "from being left on my own not knowing how I was going to get back to the naval base after all the trouble that had already occurred to having the car accident itself".

"Coming to New Zealand should have been one of the most fantastic experiences of my life, but because of something that was brought about because of circumstances that weren't entirely my fault, I spent the majority of my time in fear of losing my career."

Without the discharge, Chief Petty Officer Cobby said, she could have lost her job and opportunities "that have arisen for me after 11 years of service during which time I have made the rate of CPO [chief petty officer]."

The judge banned her from driving for the duration of her stay in New Zealand and ordered her to pay $10,000 in damages, plus court fees.

Documents released to the Herald on Sunday showed the case went to the Chief of Defence Force, Lieutenant General Jerry Mateparae, and Defence Minister Wayne Mapp.

Chief Petty Officer Cobby said there had been other cases involving NZ Navy personnel escaping conviction.

The Navy had informed her of the possibility of receiving a discharge without conviction "as I was unaware there was such a thing".