According to reports from users on Twitter, O2 has started blocking access to a lengthy list of websites, and requesting users authenticate themselves as adults by making a small charge on their credit cards, which is then credited to the user’s account.
As well as failing to notify users about the changes, many business users have expressed anger that they have had to use their personal credit cards to regain access to websites.
Perhaps worse, reports are coming in from users of non-adult websites including a farmer's fresh foods exchange, a car enthusiast's site and other clearly non-adult portals. Complaints have been made by the owners of websites, as well as their users, Infosecurity understands.
According to the Bitterwallet consumer reports site, Jalopnik, a Gawker-owned site about cars has been content blocked, whilst the NeoWin newswire reports that the lovefre.sh farmer's markets foods site has also been blocked.
What complicates matters is that the site is central to an iPhone app that O2 is promoting on its service.
NeoWin quotes Mark Spofforth of the Lovefresh site as saying that, when O2 users install his app on their iPhones, they end up being directed to a blank page.
Spofforth said that the problem only affects users of his app on the O2 network. "The problem is that most iPhones in the UK are on O2," he told the newswire adding: "I'm despondent about it. It's just crippling."
O2 responded to complaints on Twitter with its own response:
"This is solely to ensure that children are protected from inappropriate content when using the internet on their phones. That's why we require customers to prove they are over 18 before they can use these sites."
Unconfirmed reports over the weekend suggest that O2 is a using a master reference directory from the ICMB, the independent mobile classification body, although Infosecurity understands that the same directories are used by other carriers without problem.
iPhone and other O2 smartphone users report that the content block does not appears to affect non-native browsers on the iPhone, most notably Opera, nor does it affect WiFi-based web surfing.
The Guardian quotes O2 as acknowledging that people would have found it inconvenient and apologising for the lack of publicity for the introduction of the scheme.
"It could have been handled better", a spokesperson said.