He said the next step was for the boards to consider the proposals and select a preferred provider.
"The impact on current staff and services will be known once the boards make these decisions. We have made it clear that we expect as many DHB roles as possible to be retained," Mr Milne said.
Virginia Hope, chairwoman of Hutt Valley and Capital & Coast DHBs, said the boards believed there would be significant benefits with one provider.
"When someone is unwell, their GP often has blood or specimen samples taken.
"If the patient then requires hospital treatment, many of these tests are repeated because the hospital specialists can't easily access the community laboratory results."
She said a combined lab service would avoid unnecessary duplication and patient discomfort. It would also benefit health workers by having one consistent process.
The new service is expected to start November 2015.