He said the hospitals' own assessment of lab services found only minor issues: "Privatising the laboratories on the type of assumptions and faulty thinking we're seeing would be like taking your car to the wrecker because it has a broken headlight."
New Zealand Medical Association chairman Mark Peterson said it was understood the DHBs were looking to cut costs.
"[But] this issue is too important to risk the disruption and challenges that would inevitably follow a merger or transition of these services to a private provider," he said.
"As ASMS points out, current laboratory services are not 'broke' and do not need 'fixing', but require only fine-tuning."
He said a similar move at Mid Central DHB hadn't resulted in major savings and it had taken years to establish a shared workforce culture.
The DHBs' Laboratory Services Strategy shows services in the region are working reasonably well but certain services need to be "fine tuned" to improve efficiency.
Hutt Valley and Wairarapa DHBs chief executive Graham Dyer told Radio NZ they were in the middle of a commercial process and it would be inappropriate to discuss it.
DHBs are due to make a decision on a provider next month.
