Marilyn Davenport, a tea party activist and elected member of the central committee of the Republican Party of Orange County, said she will not heed calls to resign.
The controversial photo shows the president's face superimposed over the head of a baby chimp. The caption beneath the picture read, "Now you know why no birth certificate."
"I was shocked and offended and I immediately replied to her and told her that this was dripping with racism," said Scott Baugh, chairman of the RPOC. "It was sent in poor taste and she should never send an email like that to me again.
"She gave me no response," Baugh added.
Baugh said someone on the 73-member committee leaked the email to the OC Weekly.
Davenport said she has no plans to resign.
"I'm sorry if my email offended anyone, I simply found it amusing regarding the character of Obama and all the questions surrounding his origin of birth," she wrote to committee members. "In no way did I even consider the fact he's half black when I sent out the email. In fact, the thought never entered my mind until one or two other people tried to make this about race."
Civil rights activists called on Davenport to step down and for the Republican party to apologize directly to the president.
"It's vile, it's despicable and on top of that, it's racist. It's a racist slap at the president," said Earl Ofari Hutchinson, president of the Los Angeles Urban Policy Roundtable. "We are accepting nothing less than Marilyn Davenport resignation, immediately."
The California NAACP through its president, Alice Huffman, issued a statement Sunday saying the cartoon is "racist, outrageous and disrespectful."
"There are no ifs, ands, or buts about this cartoon, it is absolutely and positively racist in nature," the statement said. "There is no way that depicting the President of the United States as less than human can be considered anything but a racist act. History has shown that Blacks have been depicted in this fashion in the past to degrade African Americans as not human. Anyone who does not know this history is either ignorant, had their head buried in the sand; or as we at the NAACP believe - Simply Racist."
Baugh has called for an ethics committee hearing and says Davenport should resign.
"Anybody who crosses a line that is this bright has no business being an elected official representing other people, holding yourself out as a person of trust to make decisions on the behalf of the party," Baugh said. "It was so outrageous, it warrants a resignation."
Calls to reach Davenport for comment were unsuccessful.
City News Service contributed to this report.