The New Zealand Transport Age' />

A legal loophole allows rental companies and their foreign customers to dodge tolls on Auckland's Northern Gateway.

The New Zealand Transport Agency wrote off $13,000 from motorists who skipped the country without paying in the second half of last year.

Rental car companies are exempt from unpaid tolls if they fill out statutory declarations saying other people were driving at the gateway.

NZTA spokesman Andrew Knackstedt said rental companies could automatically charge infringement notices - such as speeding and parking offences - to customer credit cards.

But legally a toll payment notice is not an infringement.

The NZTA received 5864 statutory declarations for unpaid tolls in the six months to December 31. Most were from rental companies. Almost half were for overseas drivers and were written off due to the cost of collecting them.

AA spokesman Simon Lambourne said it was "outrageous" that rental car companies were not being held liable.

NZTA's Brett Dooley said the Transport Ministry had been asked to review the law to see if rental companies could be allowed to pass tolls on to customers. Rental Vehicle Association chief Raewyn Bleakley said statutory declarations allowed companies to pass liability on to drivers and she did not support a law change.

Drivers have paid more than $20 million in tolls since the 7.5km road between Orewa and Puhoi opened in January 2009.