Yahoo UK has updated its instant messaging chat service software to disallow access to certain adult Yahoo chat rooms, or Yahoo Clubs as they are called, located in the US.

"It's not 'blocking' access per se. Users can still obviously access US chat through Yahoo's US chat site. As part of our general push to localize content, we are also attacking the problem of undesirable content globally. It's part of our constant evaluation of our service," said Sue Jackson, a spokeswoman for Yahoo UK.

The change, which still allows Yahoo UK & Ireland users to access adult chat rooms that are based in the UK and Ireland, occurred "within the last month", Jackson said.

Jackson said Yahoo UK & Ireland has been working closely with children's charities, and internet watchdog groups such as ChildNet and the Internet Watch Foundation (IWF), on ways to improve child safety. It made the decision to block access to non-UK adult chat rooms after consultations with those groups.

The move comes amid much discussion and publicity over the busting of child pornography ring the Wonderland Club, which the British police has called the world's largest organized internet child pornography ring.

Portals are gaining a problematic train of complaints about this issue. Only last month MSN was pilloried for failing to keep proper tabs on its Teen chat rooms.