According to Politico, Attkisson had "grown frustrated with what she saw as the network's liberal bias." She also lamented that the network did not spend enough time and resources on investigative reporting and catered too much to its corporate sponsors.
Sources at CBS told Politico that Attkisson's pursuit of investigations into the Obama administration, namely Fast and Furious and Benghazi, had led to some tension at the network.
CBS sources told the Washington Post that Attkisson was frustrated that her pieces were not making "The CBS Evening News" frequently.
According to an analysis by the "Tyndall Report", her stories were featured less on the evening broadcast starting in 2009, and in 2013 she only got about a third of the air time she previously obtained.
“She was obviously being sidelined,” Tyndall told the Washington Post.
In 2012 Attkisson won the conservative watchdog group Accuracy in Media's Reed Irvine Accuracy in Media Award, which typically goes to conservative outlets.
The longtime CBS reporter also won two Emmys for her investigative reports on the Fast and Furious scandal and on the fundraising of a Republican freshman.
Attkisson told Politico that her resignation was "amicable," and thanked CBS in a Monday statement.
“It’s been one of life’s great privileges to work at CBS News, and I’m sincerely grateful for the many opportunities I’ve had,” Attkisson said in a statement, according to the Washington Post.
Sonya McNair, a spokesperson for CBS News, said Attkisson was leaving to "pursue other endeavors."
“We appreciate her many contributions and we wish her well," McNair told Politico in a statement.
Attkisson is working on a book currently titled "Stonewalled: One Reporter's Fight for Truth in Obama's Washington" about her experience reporting on the Obama administration.