ATLANTA — A longtime aide to Jimmy Carter has resigned from the Carter Center think tank, calling the former president’s new book on Israel and the Arabs one-sided and filled with errors.

The Carter Center’s first executive director and founder of its Middle East program, Kenneth Stein, sent a letter that bluntly criticized the book to Mr. Carter and others.

Mr. 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. Mr. Carter’s spokeswoman, Deanna Congileo, said the former president stands by the book.

Mr. Stein, who is also director of the Institute for the Study of Modern Israel at Emory University, did not immediately return a call Wednesday.

Mr. Carter issued a brief statement saying that Mr. Stein had not been actively involved with the center for more than 12 years and was not involved with the new book. Mr. Carter did not directly address Mr. Stein’s allegations.

It is not the first time Messrs. Carter and Stein have disagreed over Middle East policy, Douglas Brinkley said. Mr. Brinkley is a professor of history at Tulane University and the author of the 1988 biography of Mr. Carter, “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,” Mr. Brinkley said. Mr. Stein “doesn’t trust the Palestinians as much as Carter.”