The alleged driver has since been found and arrested.
The spokeswoman said the car was never going at particularly high speed because of what appeared to be a flat tyre, but police did not follow the car onto the motorway.
There had been nothing to indicate the car was stolen when the officer approached the driver initially.
Witness Yvonne Worboys said she was heading towards the motorway from Central Park Drive when the fleeing car came from behind her, almost hitting the back of her car. It was followed by two police cars.
"He then headed towards the motorway. When we came down the on-ramp to the motorway, citybound, we saw the police lights heading towards Lincoln Rd westbound but no car. I went to merge and he came straight towards us and missed my car by about a metre. There was smoke pouring from the front driver's side tyre."
Another woman, on the motorway during the chase, said: "I saw the guy driving down the motorway just after the Te Atatu offramp going the wrong way and saw him jump out by the Royal Rd overbridge. I saw maybe five to 10 cop cars giving chase down my side -the correct side - of the motorway while keeping pace with the guy going down the other side.
"They definitely hadn't called off the chase when he jumped out of his car. They still all had their lights going and were following him."
Michael Keys said he was sitting in his car at the lights on Central Park Drive when the dark grey Mazda 6 overtook the traffic on grass and on the footpath.
"Two minutes later as we were heading down the on ramp citybound at Lincoln, you could see the police entourage on the westbound side, it was at that point the Mazda 6, with a tyre blown out, was coming straight at us as we merged onto the motorway. Subsequently we swerved toward the left-hand side barrier as he went racing by.
"Driving into 100km/h traffic head-on is a man with a death wish."
