Labour's Sue Moroney says she does not want the drink driving limit to go back to its old level, despite concerns about how police are using their resources.

Labour transport spokeswoman Sue Moroney has defended her criticism of the lower drink-driving limit, saying she does not want the limit raised but police should focus on "big bad dangerous drivers" instead.

Official figures show there has been only one confirmed road death in which the driver at fault had drunk enough alcohol to put them between the new and old drink-driving limits.

Moroney said the figures showed that the Government was diverting police resources to target good drivers for fine revenue.

However, Associate Transport Minister Craig Foss said he was "comfortable" with the lowered limits and believed they had already made a difference.

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"Our roads are safer, the culture of drink driving has changed dramatically…

"Some lives have been saved - it's hard to say how many lives have been saved, of course - but we're quite comfortable with where it is at the moment."

Foss said the road toll was "still much much much too high", but the lower limits would help to address that.

"Anything we can do to help lower that road toll or the risk around it, we should be doing."

He was surprised by Moroney's stance, given Labour had been "quite vocal" on lowering the drink driving limits.

'BIG BAD DANGEROUS DRIVERS'

Moroney said she did not want the limit to be raised to its original level, but police needed to focus their stretched resources on more serious offenders.

"What I'm concerned about is because the police are cash-strapped under this government, the resources are going in the wrong direction and while the big bad dangerous drivers are continuing to cause an increased road toll, the resources are being used on the minor offences instead."

Asked whether police were putting too much focus on drink-drivers, Moroney said, "It could well be that's the case."

Drink-drivers at lower levels were "not what's driving the road toll to go up", and it was unclear whether the limit had actually saved lives.

"We're hopeful that it has, but the road toll has gone up, and that's the defining answer about whether it actually has worked or not."

Moroney said police needed to be properly funded, and to focus on people who were "well past the drinking limit and well past the speeding limit".

"I'm concerned about making sure...that the resources are put into the places where the high speeds have been travelled and the outrageous amounts of alcohol have been consumed, that we're dealing with that, because we've got a road toll going up against the trend."

THE DEATH TOLL, AND THE LAW

A total of 320 people died on the roads last year, compared with 294 in 2014. There have been 52 road deaths so far this year, against 49 by the same time last year.

Before the new limit of 50 milligrams of alcohol per 100 millilitres of blood, or 250 micrograms of alcohol per litre of breath, was introduced in December 2014, the Ministry of Transport estimated it would save three lives a year, as well as 64 minor and serious injuries.

The old limit, of 80mg or 400mcg, remains the threshold for a criminal prosecution. Drivers caught between the two limits receive a $200 fine, 50 demerit points, and are banned from driving for the next 12 hours.

The single death caused by a driver between the two limits was in February 2015. Police could not say whether the driver's alcohol consumption was the lead cause of the crash.

Between December 2014 and August 2015, police issued 4917 infringement notices to motorists caught between the new and old limits.

A police headquarters spokeswoman there were "promising signs" the law change might be influencing drivers' behaviour because, since October 2015, almost 2500 fewer drivers had been caught over the old limit.

The Ministry of Transport will undertake a review of the lower drink-driving limit once it has three years of data.