Vehicle inspectors fear an automotive version of the "leaky homes" saga if roadworthiness tests for trucks and buses are deregulated.

The country's largest inspection company, Vehicle Testing NZ, believes the Government is poised to allow repair workshops and even some trucking companies to issue certificates of fitness.

Although repairers can now issue warrants of fitness for cars and other light vehicles, inspections of trucks and buses are limited to just three organisations under appointment to the Government's Transport Agency.

Vehicle Testing chief executive Mike Walsh, whose company conducts 86 per cent of all heavy vehicle safety inspections through a national network of 85 stations, said yesterday that the independence of the process was at risk from changes due to be announced by the Government in the next few days.


He cited leaky buildings and taxi deregulation as examples of what could go wrong when industries were given greater freedom to set their own standards.

It was no coincidence that New Zealand had one of the world's best heavy vehicle safety records, as the cornerstone of its regulatory system was the independence of inspectors.

"We have no interest in repairs and there's never a question that standards or safety will be compromised by commercial pressure," Mr Walsh said.

"As people travel on the roads this summer, they need to look at the trucks on the other side of the centre line and ask themselves how much deregulation and increased road risk they're prepared to live with."

He said 32 per cent of trucks failed inspections, including many which had already passed through vehicle workshops.

A spokeswoman for Associate Transport Minister Simon Bridges, who is driving reforms to vehicle licensing, said he had no comment ahead of Government announcements expected before the end of the year.

But Mr Walsh said he was disappointed that economic advisers to the Ministry of Transport appeared from a meeting on Thursday to have under-estimated potential risks in their enthusiasm for perceived cost savings.

They had told him deregulating the certification process for heavy vehicles would build to an annual saving of $29 million within six years, a claim that his organisation disputed.

Road Transport Forum chief executive Ken Shirley said his members generally favoured an independent testing regime, but also wanted better service, including more weekend inspections to reduce costly interruptions to freight operations.

They believed independence could be preserved by allowing repair workshops, including those run by larger trucking companies, to conduct inspections under the supervision of certified engineers.

He said the forum was involved in discussions with the Institution of Professional Engineers to that end, and noted that Vehicle Testing was owned by the Motor Trade Association, which represents vehicle repairers as well as service stations.

Mr Walsh acknowledged it was "very easy to dismiss our comment as self-interest or even scaremongering - but the reality is that we're appointed by the NZ Transport Agency to provide a nationwide service that ensures trucks aresafe".

Relaxing inspections was likely to see many Vehicle Testing NZ stations closing or reducing services as competitors began nibbling away at their business, and there was only so much money to be saved without sacrificing standards.