LOS ANGELES, California (CNN) -- Former CBS News anchor Dan Rather says the $70 million lawsuit he filed Wednesday against his former employer is an effort to strike a blow against political and corporate influence that he believes threatens the independence of American journalism.

Dan Rather, here in July 2006, said that corporate and political influence may cause a chilling effect on journalism.

"This is the right stand, at the right time, about the right issue," Rather told CNN's Larry King Thursday night, in his first TV interview since filing the suit. "We have to, somehow, get back to integrity in the news and somehow at least alleviate, if not eliminate, these big corporate and big government pressures."

"You can't have freedom of the press if you're going to have large, big corporations and big government intruding and intimidating in newsrooms. The chilling effect on investigative reporting is going to be something we don't want to see," he said.

Rather's breach of contract suit charges that CBS made him the scapegoat when the network came under intense criticism over a September 2004 "60 Minutes II" story challenging President Bush's service in the Texas Air National Guard during the Vietnam War.

Immediately after the story aired, critics began questioning the authenticity of documents used to buttress allegations that Bush did not fulfill his military commitments. Rather, who narrated the disputed piece, became the target of fierce criticism from conservative partisans who believed the story was an attempt to influence the 2004 presidential race.

Six months later, he stepped down from the anchor chair he had occupied for nearly a quarter century -- a departure he says was not voluntary.

In his interview with King, Rather again defended the accuracy of the story and said "I think there's a lot more in the president's military record that we don't know about."

"Nobody to this day has proved these documents were fraudulent," Rather said. "The story was true."

He also said an independent investigative panel commissioned by CBS, which issued a report highly critical of the story, was a "fraud."

"It was a set-up," Rather said of the investigation, headed by former Attorney General Richard Thornburgh and former Associated Press chief Louis Boccardi, which led to the firing of a producer and the resignations of three executives. "It was designed to achieve a certain result so that the corporation would be exonerated."

Rather's suit alleges that management at CBS and its then parent company, Viacom, shifted blame to him to pacify the White House and that on the day after Bush was re-elected, he was informed he would be removed as anchor of the CBS Evening News.

The suit maintains that inaccuracies in the National Guard report have "never been established," but, even if there were errors, he was not responsible for them because he "played largely a supervisory role" in the production of the broadcast and was assured by others that the documents had been authenticated.

After initially defending the piece, CBS later retracted it, and Rather later made an on-air statement admitting the network couldn't vouch for the authenticity of the documents and calling the decision to air the story a "mistake in judgment."

However, Rather now charges in his lawsuit that he was "coerced" by CBS management "into publicly apologizing and taking blame for alleged journalistic errors in the broadcast."

Rather told King that he agreed to read the on-air apology -- largely written by other people -- to "play team" and help the organization where he had worked for more than 40 years.

"I didn't want to apologize. I didn't think we should apologize," he said.

He also said he didn't realize at the time that the apology was part of an effort by management to "make sure that they shifted whatever blame there was going to be ... away from themselves and put it on me and some other good people in the news division."

Rather said that in the weeks leading up to broadcast, he was not deeply involved in National Guard story because he was extremely busy covering a number of other major news stories, including a hurricane and the Republican National Convention.

He also said he was not invited to the final screening of the piece before it aired, which was attended by two corporate attorneys and a host of CBS executives, including Andrew Heyward, then president of the news division.

"I depended on a team of people to vet it," he said. "Didn't happen."

Rather said he is not interested in gaining financially from the suit and will donate a "substantial part" of any damages he collects to journalism organizations who work to keep "hard-nosed investigative reporting alive."

Rather's suit names as defendants CBS and its CEO, Leslie Moonves; Heyward; and Viacom and its CEO, Sumner Redstone.

Reacting to the suit, CBS issued a statement saying "these complaints are old news, and this lawsuit is without merit." Contacted for their reaction, Moonves and Heyward referred CNN to the CBS statement; Viacom and Redstone refused comment. E-mail to a friend

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