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A 14-year-old Whangarei girl, legally too young to have sex, buy alcohol, or drive a car, has shocked police who this week caught her behind the wheel, five times the drink-drive limit and four months pregnant.

The teen was spotted by police driving "erratically" on Kamo Rd in Whangarei about 11pm on Tuesday.

She allegedly provided officers with a false name, which she had problems spelling, before giving a breath-alcohol reading of 828 micrograms of alcohol per litre of breath - more than five times the youth drink-driving limit of 150mcg, and more than twice the adult limit of 400mcg.

But officers say the situation is hardly surprising, given that alcohol is readily available to youths, and teen drink-driving is on the rise.

Whangarei-Kaipara area commander Inspector Paul Dimery said that while teenage drinking, underage driving and underage pregnancy were common, the girl's combination of all three had come as a shock.

The girl's high breath-alcohol reading was also disturbing.

"That is exceptionally high for an adult. For a 14-year-old it's quite astounding. For a pregnant 14-year-old, it's almost disgusting," he said. "What's the expected outcome for that child? You've got children having children. They have no understanding of the harm that they're causing their unborn child.

"I can't comment on specifics but clearly, anyone that's 14, is pregnant, is drink-driving - the issues probably go a lot deeper."

Mr Dimery said teens and adults who bought alcohol for underage people were contributing to the problem teen drinking culture.

The ready-to-drink alcohol industry also had a lot to answer for with teens finding drinks easy to swallow, compared with decades ago when drinkers had to "get a taste" for beer and wine, he said.

"The reality is that since the legal drinking age came down there has been a huge increase in teenage drinking and the age has dropped dramatically because it's easier to pretend you're 18 than it was to pretend you're 20. I have no doubt the drop in drinking age contributes to this type of behaviour."

Family First lobby group director Bob McCoskrie said the girl's situation showed a lack of proper boundaries in her discipline.

"There's a huge issue of lack of supervision for this case," he said.

The case highlighted a lack of pre and post-natal advice for women as well as a lack of debate around the country's attitude to alcohol, Mr McCoskrie said.

New Zealand had extremely high teen pregnancy and binge drinking rates, and the girl's case could be just the "tip of the iceberg", he said.

Child, Youth and Family general manager operations Lorraine Williams said the organisation had been "trying to work with this teenager but it has been very difficult".