The older brother of JonBenét Ramsey is suing the US television network CBS and others for $750m (£610m), saying his reputation was ruined after a television series concluded he killed his six-year-old sister two decades ago.

In the lawsuit filed on Wednesday, Burke Ramsey, 29, claims the network, its production company and the experts interviewed in the series on the unsolved murder conspired to defame him for publicity and profit. The series, called The Case of JonBenét Ramsey, aired in September ahead of the 20th anniversary of JonBenét’s death.

The beauty pageant star was found dead in the basement of her family’s home in Boulder, Colorado, the day after Christmas in 1996. A prosecutor cleared her parents and brother in 2008 based on DNA evidence. But the district attorney currently overseeing the case has said it was premature to exonerate the Ramseys and ordered additional tests using new DNA testing technology that authorities hope will further the investigation.

Police have collected and studied thousands of pieces of evidence and say the case remains open.

CBS spokesman Dustin Smith declined to comment on the lawsuit, which is the second Ramsey has filed over the television series. In October, Ramsey sued a forensic pathologist featured on the show who said he bludgeoned his sister to death. The pathologist is also named in the latest lawsuit, which was filed in Michigan, where Ramsey lives.

The new lawsuit says CBS and its featured experts set out to conduct a “sham reinvestigation” of the murder with “the preconceived storyline” that Ramsey killed his sister and conspired with his parents to cover it up.

“The accusation that Burke Ramsey killed his sister was based on a compilation of lies, half-truths, manufactured information, and the intentional omission and avoidance of truthful information about the murder of JonBenét Ramsey,” the lawsuit says.