The number of websites that feature pornographic images of children fell by 10 percent in 2008, says the Internet Watch Foundation.

According to the web charity, 74 percent of child sexual abuse websites were commercial and sold inappropriate images of children, while 69 percent of the child abuse images found online featured children thought to be 10 or younger.

"These websites, although reducing in number, represent an extremely serious problem," said IWF Chief Executive Peter Robbins.

The IWF also said that as a result of efforts by itself and the police, it was harder for commercial sites to continue with many being shut down within hours.