"We Googled the word 'porn' and clicked on a handful of sites. They were all blocked by content-filtering," the article said.
"However, a simple Google image search for "porn" brought up dozens of explicit and non-pixelated images. The search results seemed entirely unfiltered."
Auckland Council's North and West Libraries Customer Experience manager Darryl Soljan said all libraries used blocking and filtering software that was regularly updated.
"As with such software globally, nothing is 100% fool proof," he said.
Staff will intervene if they see material being accessed, he said.
Mr Soljan said there had been no operational changes to address the issue since it was raised by the Flagstaff late last week.
The terms of conditions of the internet - that had to be accepted before the service can be used - state that no objectionable material is allowed to be accessed.
Despite being able to view the images, if you clicked on them the sites were blocked, he said.
"Because these images are viewed on the search engine website, the only way to prevent the situation you describe would be to blacklist the search engine entirely. This would disadvantage a huge number of our customers and contravene the New Zealand Bill of Rights."
While the Devonport issue was the one initially raised, Mr Soljan confirmed the loophole applied city-wide.
"Auckland Libraries' free wi-fi platform is part of the same AucklandOn platform...which the council provides at various hotspots around Auckland."
NetSafe Executive Director Martin Cocker said there was software available that would filter the images, but that it was not necessarily the council's duty to provide such strict content management.
"It's not that it can't be done - up and down New Zealand there are thousands of schools running on filters that are doing a better job than it sounds like this one is doing," he said.
Mr Cocker said only some type of pornography was illegal, so as long as "objectionable" images - like those involving children or violence - were not available, the search results would be legal.
"If people want to access pornography then they will access it. If you block the sources they will just find another one, but it is important to make a good go of removing that sort of content."