I would like to legally sue the webmasters and one mr.vikas dubey, boisar for posting defematory messages?

The webmasters of consumercomplaints.in have allowed one mr.vikas dubey of boisar to post defamatory and baseless allegations against my friend mr.muthreja suresh of mumbai. What legal action can I and my friend take against the webmasters and mr.vikas dubey ? How can I get the postings removed legally and forever ? Please help.