Cover up Negative Comments on Internet

Our client has had a competitor write slanderous comments about their company on the internet. Previously we had a service provider create hundreds of listings on internet advertising sites, bulletin boards, etc. about a make believe company with the same name. This knocked the slanderous comments down to pages 4 and lower on google and yahoo searches. Unfortunately the competitor has created more slanderous comments, using multiple comments on a thread on the same page. Now the search results now show up on page 1 again. So we are looking for some creative input here. What can you do to hide these postings and comments. They are on simple web pages like [login to view URL] ; [login to view URL] ; [login to view URL] . We have had some success in having these sites remove the slander. But what we are looking for is a better solution, one that will make it nearly impossible to appear again. Keep in mind, we do not want the clients website search result to disappear. We will only disclose our clients name to the winner of this project. This job must be started right away and we are looking for fast results. What is your solution?