In a letter of resignation obtained by the Associated Press, the openly anti-abortion Handel said she supported Komen's strategy of ending grants to the women's health service provider due to a government investigation of whether it uses federal funds to pay for abortions.
More from GlobalPost: Susan G. Komen ends funding for Planned Parenthood
"I am deeply disappointed by the gross mischaracterizations of the strategy, its rationale, and my involvement in it," she is quoted as saying. "I openly acknowledge my role in the matter and continue to believe our decision was the best one for Komen's future and the women we serve."
Until now, Handel had avoided making any public statement on her involvement in the decision.
According to her letter, reprinted in full on the Atlanta Journal Constitution's website, Komen's concerns about the controversy related to Planned Parenthood date long back, and the decision to "update our funding model" was taken before Handel began working for the foundation. However, it was subsequently "fully vetted by every appropriate level within the organization," she wrote.
She insisted the decision was based not on ideology but "Komen’s mission and how to better serve women," and expressed her disappointment that it had since been "turned into something about politics."
Finally, Handel writes that she will not accept a proposed severance package.
She is due to give a press conference later today.
More from GlobalPost: Komen apologizes, says it will continue to fund Planned Parenthood
Handel joined Komen in early 2011, after a failed bid to become the Republican governor of Georgia in 2010. During that campaign, she publicly expressed her opposition to abortion and to Planned Parenthood.
She was a driving force behind the funding cuts, a Komen source told the AP, despite the insistence of the charity's founder, Nancy Brinker, that Handel did not have a "significant role" in the policy change.
Another unnamed Komen insider told the Huffington Post:
"Karen Handel was the prime instigator of this effort, and she herself personally came up with investigation criteria. She said, 'If we just say it's about investigations, we can defund Planned Parenthood and no one can blame us for being political.'"
Komen senior public health official, Mollie Williams, reportedly resigned in protest when the cuts were approved. Williams declined to comment, however.
After widespread outcry when the cuts were announced on Feb. 1, Komen apologized and said it would continue to fund Planned Parenthood.