Kenneth Stein, the Carter Center's first executive director and founder of its Middle East program, sent a letter that bluntly criticized the book to Carter and others.
Stein wrote that the book, "Palestine: Peace, Not Apartheid," was replete with factual errors, material copied from other sources and "simply invented segments," according to an excerpt of the letter published by the Atlanta Journal-Constitution.
Deanna Congileo, Carter's spokeswoman, said the former president stands by the book.
Stein, who is also director of the Institute for the Study of Modern Israel at Emory University, did not immediately return a call Wednesday.
Carter issued a brief statement saying that Stein had not been actively involved with the center for more than 12 years and was not involved with the new book. Carter did not directly address Stein's allegations.
It is not the first time Carter and Stein have disagreed over Middle East policy, said Douglas Brinkley, a professor of history at Tulane University and the author of the 1988 Carter biography, "The Unfinished Presidency."
"They've never been on the same page in the Middle East. They've been in an almost constant state of disagreement," Brinkley said. Stein "doesn't trust the Palestinians as much as Carter."
Brinkley said he has read Carter's new book but would not address Stein's accusations.