Cape Town — ID leader Patricia de Lille has urged the government to regulate internet blog sites and the popular Mxit text message service.

De Lille also indicated that the ID will ask the National Intelligence Agency to try to track down the author of allegedly defamatory statements about the party's Simon Grindrod on an internet blog.

She said blogs allowed anonymous individuals to post defamatory comments without the legal consequences they would face in mainstream media.

She cited a blog which had attacked Grindrod.

"He reported this matter to the Caledon Square police and they are currently investigating it," she said.

"Because ... we couldn't trace the author of the defamatory statements, we will also ask the NIA to investigate.

"The only way to put a stop to this is to use every legal option to hold not only the website, but also the perpetrator, responsible. This kind of thing must not go unchallenged."

She said she was also concerned about "a surge in activity among young children on Mxit, which makes them vulnerable to sexual predators and paedophiles".

"This has gone too far and it is time for government to intervene to protect our most vulnerable. The right to freedom of expression is not absolute," De Lille said.

Last year, concerns were raised by school principals and parents battling to cope with children who seemed addicted to the messaging service.

Some schools had reportedly banned cellphones, and some parents were monitoring their children's use of Mxit, which charges only 2c per message.