He added that he hoped people would decide they did not want to enhance their breasts but would “become more comfortable from the inside out”.
But he added “the evidence is growing” the technique could work.
“I believe that it can happen in theory and I think it’s definitely worth investing the time of evidence and research into hypnosis generally.”
The interview contradicts claims Polanski has made since becoming leader of the Green Party.
In September last year he was asked on Good Morning Britain if he believed at the time that hypnosis could enlarge a woman’s breasts.
“No,” he said.
“I was misrepresented, I apologised a day later,” he added.
The same month, when asked about the Sun piece on the Pod Save the UK podcast, he said: “I went out on BBC Radio the next day, so not twelve years later when I became a politician, but literally the next day to go ‘this article doesn’t represent me’.”
As deputy leader of the Green Party, he told LBC radio he “never believed that” women’s breasts can be enlarged through hypnotherapy.
“I apologised immediately the day after the article 11 years ago to say that doesn’t represent my work and that I don’t stand by that article. I apologised because I recognised that would be offensive to people,” he said.
Commenting on the emergence of the Radio Humberside interview, a Labour Party source said: “Zack Polanski’s ego might have got bigger, but nothing else has.
“It’s now clear that his pretence to have been misrepresented over his breast enlargement hypnosis scam was absolute nonsense – he got called out years later, and he lied about it.
“You can’t trust a word he says – he’ll say whatever he thinks you want to hear.”