"Many of us have worked with Director Comey; all of us respect him. But his unprecedented decision to publicly comment on evidence in what may be an ongoing inquiry just eleven days before a presidential election leaves us both astonished and perplexed," the letter said.
Comey sent a letter to key leaders in Congress Friday informing the members that the bureau was reviewing additional emails possibly related to Hillary Clinton's personal server, after it learned of new information that might be relevant to the case.
The letter sent by former DOJ officials was circulated by the Clinton camp Sunday.
The authors of the letter said they were "moved" to speak out publicly because Comey's action violated "settled" DOJ tenets. Justice Department officials are instructed to refrain from commenting publicly on pending investigations except in "exceptional circumstances," as well as to "exercise heightened restraint near the time of a primary or general election," said the letter.
"We cannot recall a prior instance where a senior Justice Department official— Republican or Democrat—has, on the eve of a major election, issued a public statement where the mere disclosure of information may impact the election’s outcome, yet the official acknowledges the information to be examined may not be significant or new," they wrote.
The nearly 100 former DOJ officials who signed on to the letter, wrote that Comey's letter to Congress was inconsistent with prevailing department policy and that it broke with longstanding practices followed during past elections.
"Perhaps most troubling to us is the precedent set by this departure from the Department’s widely-respected, non-partisan traditions," they wrote.
It is long-standing DOJ tradition not to take investigative actions close to an election that could potentially influence the outcome of an election.
The officials said that while they don't question Comey's motives, his disclosure has invited "considerable, uninformed public speculation about the significance of newly-discovered material."
Given that, they called on the FBI to release information that provides a "full and complete picture" of the recently discovered material.
He also sent a letter to FBI staff explaining his rationale for sharing the new information with Congress. He wrote that he was briefed about the emails on Thursday and agreed with the investigative team's recommendation that steps should be taken to obtain and review them, since they appeared to be "pertinent" to the investigation.
"Of course, we don't ordinarily tell Congress about ongoing investigations, but here I feel an obligation to do so given that I testified repeatedly in recent months that our investigation was completed. I also think it would be misleading to the American people were we not to supplement the record," he wrote to employees.
Current Department of Justice officials also urged the FBI director to hold off, according to sources familiar with the matter.
After learning that the FBI was planning to send the memo to Congress, it was "made abundantly clear" to the FBI by senior DOJ officials, including Attorney General Loretta Lynch, that the DOJ officials had serious concerns and that the move would be inconsistent with DOJ policy, one source said. Comey however "decided to move forward anyway," the source said.
Comey has reached out to top Republicans and Democrats in Congress to brief them on the new review, but has yet to speak out publicly on the matter.
ABC News' Mike Levine, Jack Date and Ben Seigel contributed to this story.