The Minister of Police's branded car was on the road for months illegally.
Stuart Nash already admitted yesterday that he had been driving with an expired registration.
Now it turns out his diesel-powered car was on the road without paying the fuel levy for at least two months.
On Wednesday night his Volkswagen Amorak was still showing as owing money to NZ Transport Agency for the road user charges.
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NZTA's guidance on road user charges states: "It is your responsibility to ensure that your vehicle remains legal on the road."
Nash said the road user charges were currently paid although did not respond to questions as to whether the payment was made after the Herald raised the issue with his ministerial office.
He said: "If I receive an infringement notice I will of course pay it."
It's a double-blunder for Nash, with police responsible for enforcing both road user charges and registration.
He was initially busted by a local Facebook group when a keen-eyed member posted photographs of the car showing it was on the road with an expired registration.
The registration was valid until September 8. It wasn't renewed by Nash until after he was exposed on the Napier News on Facebook.
Nash said he renewed his registration yesterday after "a family member gave me a heads up".
The photograph displayed in the Napier News site also showed Nash had paid road user charges up to 40,000km.
But a Car Jam report on the vehicle shows the car had exceeded that distance when its odometer was recorded at 40,420km when checked for a Warrant of Fitness on August 26.
As of Wednesday evening, the Car Jam report showed the vehicle was still only paid up to a 40,000km limit even though Nash had been driving it beyond that point for at least two months.
While the fee owing is not large - at 420km it's about $35 - it is a compulsory payment for diesel vehicles, with cash going into the National Land Transport Fund to pay for the upkeep of the national roading network.
Nash's car was still carrying the out-of-date registration and road user charge certificate when spotted today.
A police spokesman said all vehicle owners should ensure vehicles have current registration, warrant of fitness and road user charges at all times.
"Any vehicle owner who is stopped by Police and found to have an expired registration, warrant of fitness or road user charges can expect enforcement action. This can take the form of either an offer of compliance or an infringement notice.
"In this instance Minister Nash was not stopped by Police and we understand he has since taken the necessary actions to renew the registration and road user charges for his vehicle."
No action would be taken, the spokesman said.
The spokesman said: "All vehicle owners can expect to be treated with fairness and consistency by New Zealand Police."
A spokesman for NZTA said the money helped pay for road improvements and maintenance, public transport, road safety, along with walking and cycling work.
"Everyone using New Zealand's roads contributes towards their upkeep."
Dog & Lemon Guide editor Clive Matthew-Wilson said the car registration and road user charges system was a "shambles".
"It's incredibly easy - as the minister has demonstrated - for it to expire. People face tickets on a daily basis for what is actually a simple oversight."
Matthew-Wilson said the system needed to fully automated so road users could save a credit card to an account that was charged when payment was due.
The best place for charges to be levied on fuel was at the pump, he said. The different levy on diesel was brought in for large trucks often run by commercial operators. "It works well for large companies with well organised financial systems."
National Party police spokesman Brett Hudson said Nash's branded car probably meant he was less likely to be pulled over and checked by police.
"If we neglect to do these things, we can expect someone in the public will call us out on it.
"It's important we all make sure we follow the law and register our vehicles, and if we have Road User Charges, that we pay it."
He supported Matthew-Wilson's suggestion of greater automation.
Nash is the latest in a long line of law-breaking ministers. Former Transport Minister Gerry Brownlee was fined after skipping security screening to race for a plane. While Minister of Police, former National MP John Banks was also fined after using a mobile phone on a commercial flight.