The number of random breath tests has nearly halved in Auckland in the past few years (file photo).

A "concerning" increase in drink-driving in Auckland is due to a decrease in the number of random breath tests in the region, a report has found.

The report, commissioned by Auckland Transport and carried out by international road safety advisory Whiting Moyne, said road deaths involving alcohol in Auckland had risen by 28 per cent from 2015-2017.

Meanwhile, the rate of serious injuries had risen by 31 per cent.

The report called the increase in drink-driving "most concerning" and outlined the need to return to more random breath tests across Auckland.

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Random breath testing has fallen nationwide, from three million tests being performed from 2013 to 2014 to about two million from 2016 to 2017.

In Auckland, the number of random breath tests carried out almost halved from 2013-14 to 2016-17, from 771,000 to 396,000.

The report recommended police capacity to deliver random breath tests be boosted, as well as an increase in road policing numbers.

Whiting Moyne president Eric Howard said there was a very clear link between the number of breath tests administered and drink-driving incidents.

"When we're talking about stopping drink-driving there's two different ways of deterring people – general and specific deterrence. Random breath tests fall into that general category," he said.

"The fact is as the rates of random breath testing lowered in Auckland, alcohol-related fatalities and injuries increased, [and] the road policing resources for Auckland were reduced significantly."

Police national manager of road policing Superintendent Steve Greally said in a statement police were working towards preventing death and injury on the roads.

"As road safety partners, our shared goal is making New Zealand roads safer," he said.

"Police focus is on prevention activities and enforcement of the law [and] we are in regular contact with our road safety partners to support this work."

The Labour Government announced in its 2018 Budget funding for police would be increased to nearly $300 million over four years.

That meant an extra 920 officers would be able to be hired in the coming year, along with 240 support staff.