Australian Prime Minister Kevin Rudd says he will look into the idea of appointing an online ombudsman after Facebook tribute pages were defaced with pornography and offensive comments.

Pages set up to honour slain Queensland children Trinity Bates and Elliott Fletcher have been defaced in the past fortnight.

Independent senator Nick Xenophon has proposed the appointment of an online ombudsman to deal with such incidents.

"Specifically on Nick's idea, let's look at it," Rudd told the Seven Network.

"The role of cyber crime and internet bullying on children is frankly frightening and we need to be deploying all practical measures."