An Oscar-winning filmmaker has dropped plans to make a documentary about Hillary Clinton, following protests by Republican rivals, and a planned TV miniseries about her has also been scrapped.

Charles Ferguson, who was making his film for CNN, faced criticism from Republicans that it would promote the former US secretary of state's expected 2016 presidential run, while Democrats appeared reluctant to speak to him.

"When I approached people for interviews, I discovered that nobody, and I mean nobody, was interested in helping me make this film," he wrote.

"After approaching well over a hundred people, only two persons who had ever dealt with Mrs. Clinton would agree to an on-camera interview, and I suspected that even they would back out."

Ferguson, who won an Oscar for "Inside Job," his 2010 documentary about the financial crisis, said he began with the idea of making an "ambitious, controversial, and highly visible" film which was independent and fair on the former secretary of state, senator and first lady.

But Clinton was not cooperating and some Democrats were concerned about it as a commercial venture, Ferguson said. Republicans claimed the film would promote Clinton, who is considering a 2016 White House run.

"Neither political party wanted the film made," Ferguson said.

"After painful reflection, I decided that I couldn't make a film of which I would be proud. And so I'm cancelling. (Not because of any pressure from CNN -- quite the contrary.)

"It's a victory for the Clintons, and for the money machines that both political parties have now become. But I don't think that it's a victory for the media, or for the American people," added the filmmaker, who was also nominated for an Oscar for his Iraq War documentary "No End In Sight."

Clinton has made no announcement of her plans but Republican National Committee (RNC) letters -- more than three years ahead of the next presidential election -- show the party's nervousness about a run by Clinton, who narrowly lost the Democratic nomination to Barack Obama in 2008.

Earlier this year, Republicans threatened to prevent two US television networks from carrying party primary debates if they don't abandon planned documentaries on the former first lady.

CNN reiterated the decision to scrap the project was made by Ferguson.

"Charles Ferguson has informed us that he is not moving forward with his documentary about Hillary Clinton," a CNN statement said. "Charles is an Academy Award winning director who CNN Films was excited to be working with, but we understand and respect his decision."

A few hours after Ferguson's announcement, NBC Entertainment announced that it had scrapped a planned miniseries on Clinton.

"After reviewing and prioritizing our slate of movie/miniseries development, we've decided that we will no longer continue developing the Hillary Clinton miniseries," NBC said in a statement emailed to AFP.

While two projects have been abandoned, another remains alive.

A film tentatively titled "Rodham" is listed as "in development" by director James Ponsoldt, focused on her "early years as a young lawyer in Arkansas during the Watergate scandal," according to the IMDb industry database.

"It's a very grounded, intimate story, it's not a cradle to grave biopic, it's a story about a woman in her mid-twenties who's choosing between a career and a relationship," Ponsoldt told the indiewire.com movie news website in August.

He admitted his project has also drawn responses from all sides. "I've definitely heard an earful from everyone you can imagine, politically -- right, left, people in the film business," he said.