Sir Bob Harvey has said "police now need to step up," after true-crime documentary series Black Coast Vanishings aired over the weekend.
The documentary series was released on ThreeNow on Sunday and explores the disappearance of six people in the small surfing town of Piha in west Auckland. It also speaks to women who say they have been chased through bushes and sand dunes in the area.
Sir Bob, who was the Waitākere mayor from 1992 to 2010, was driven to write an article for Metro in 2018 when he became suspicious that some of the disappearances were connected.
He said the topic was broached a couple of times before by others but without much success.
"They didn't want to do something that would affect the families greatly but of course it still affects the families greatly, that's why I did it," he said.
Sir Bob said that the cases need closure and, while he is a "big fan of the police, they behaved badly in most of these cases".
He believes that two of the cases discussed in the documentary series are red herrings and not necessarily connected to the others.
"I think Quentin [Godwin] was probably killed by his mates accidentally," he said.
Asked about the belief that it is a serial killer who connects the disappearances that he discusses in the series, Sir Bob said, "I'm not talking so much a serial killer.
"I think they've been taken, and the police now need to step up and go over exactly what they thought happened."
Sir Bob believes that Cherie Vousden did not die by falling from the cliffs, as was declared in the coroner's report.
Five years later another woman, Kim Bambus, vanished in extremely similar circumstances and Sir Bob doubts they are unconnected.
"Throw a watermelon off those cliffs and see what happens," he said.
Sir Bob urged police to reevaluate what they believe happened in a case that is still open.
"The French guy's [Éloi Rolland] case is still open, and I can't believe that the Chinese guy [Guoquan 'Laurence' Wu] and the French guy just walked into the surf on a Saturday where there are surfers and dogs.
"No backpack or shoes, nothing has been found of any of them."
Sir Bob said that he wouldn't be talking about the cases if "one thing had been found of these people."
"They simply vanished."
Black Coast Vanishings can be watched on ThreeNow.