"The way the hair has been painted in this picture, it looks like colouring in," he said.
However, the Auckland Art Gallery was more cautious, with communications officer Jade Lucas saying their art expert could not pass judgment on the painting until she had seen it.
The 88-year-old owner of the picture was indignant when told of Mr Blackley's analysis.
"As far as I'm concerned, it's by Goldie," he said firmly.
And he jumped at an Advocate offer to take him and the painting to the Auckland Art Gallery, where the head of their curatorial services team will put it under a microscope.
Meanwhile, an Onerahi reader called the paper yesterday to say he had a painting at his home which could rival the Goldie portrait of Rutene Te Uamairangi which Dame Kiri Te Kanawa sold in 2010 for $573,000, the most paid for a painting at auction in New Zealand.
He did own a Goldie but it is a print of the portrait of Te Aho-te-Rangi Wharepu of Ngati Mahuta known as A Good Joke.