Sergeant Claire Carter said the fleeing vehicle braked near Cemetery Rd, and then reversed into the pursuing police vehicle before driving off.
The police car was extensively damaged and had to be towed.
Jayden Jameson was driving through the roadworks on Maunu Rd when he had to swerve to avoid the speeding 4X4 aimed right at him on the wrong side of the road.
"I was let through by the road workers and was heading towards town. It was down to one lane," said the 18-year-old driver.
"I could see a big four-wheel-drive coming towards me on the wrong side of the road. It really started speeding up and wasn't going to slow down. I flashed my lights but had to go as far left as I could."
He believes the oncoming vehicle slipped by with only centimetres to spare, crashing through cones as it sped off.
As he waited on the side of the road he could see the flashing red and blue lights of a police car. After it went past Mr Jameson said he did a U-turn and followed. The next time he saw the police car its bonnet was crushed.
Anyone with information should call Whangarei police station on 09 430 4500 or 0800 crimestoppers.