Former U.S. Attorney General Eric Holder condemned FBI Director James Comey’s handling of the investigation into Hillary Clinton’s private email server in a Sunday Washington Post op-ed, saying that Comey must correct his “serious error” or risk undermining public faith in the U.S. justice system.

Praising Comey as a “man of integrity and honor,” Holder said he wildly overstepped and broke with both Justice Department policy by writing a “vague letter to Congress” about newly discovered emails that may be related to Clinton’s server.

“That decision was incorrect,” Holder wrote. “It violated long-standing Justice Department policies and tradition. And it ran counter to guidance that I put in place four years ago laying out the proper way to conduct investigations during an election season.”

As Holder, who spent 40 years working in the U.S. justice system and served as Obama’s attorney general from 2009 to 2015, lays out, the FBI is governed by DOJ policy preventing commenting on ongoing investigations. Longstanding policy also dictates that unnecessary action should not be taken close to Election Day that could influence a race’s outcome.

“Director Comey broke with these fundamental principles,” Holder wrote. “I fear he has unintentionally and negatively affected public trust in both the Justice Department and the FBI. And he has allowed—again without improper motive—misinformation to be spread by partisans with less pure intentions.”

Donald Trump’s campaign and senior Republicans have seized on the news, accusing Clinton of “criminal action,” though there is not yet any information about what is contained in the emails or how many are duplicates of messages that have been previously reviewed.

“Because of his decision to comment on this development before sufficient facts were known, the public has faced a torrent of conspiracy theories and misrepresentations,” Holder wrote.

The former attorney general argued that this messy situation had its roots in Comey’s July press conference announcing that he recommended that the DOJ bring no charges against Clinton—another unprecedented break with department policy.

Holder called the press conference a “stunning breach of protocol,” writing that sharing personal opinions about a high-profile, highly politicized case undermined the public’s faith in a neutral Justice Department.

“He has committed a serious error with potentially severe implications,” the former attorney general wrote of Comey’s Friday letter. “It is incumbent upon him — or the leadership of the department — to dispel the uncertainty he has created before Election Day.”