The sole occupant of the vehicle, a 53-year-old farm manager from Tuai, near Lake Waikaremoana, was thought to have reamin in the vehicle overnight.
"He had serious injuries," Mr James said.
The injured man was removed from the wreckage by firefighters and St John ambulance officers from Wairoa.
"They used ropes and a rescue basket to get him up the slope," said St John territory manager Shane Clapperton, who was on the chopper.
The ECT rescue helicopter landed on the road.
"The 4WD hit several trees and appears to have rolled several times on the way down the steep bank," Mr Clapperton said.
"The man suffered extensive, multiple injuries."
He was airlifted to Gisborne Hospital initially, then flown out to Waikato Hospital later yesterday for more specialist care.
"He is in a critical condition in our intensive care unit," a Waikato spokeswoman said this morning.
Police have an investigation under way into the crash.
"That inquiry will continue over coming days," Mr James said. "The name of the driver has not yet been released."
