Rep. Adam SchiffAdam Bennett SchiffPelosi, Democrats launch Mueller messaging blitz Mueller testimony could be frustrating for both parties Hillicon Valley: Equifax to pay up to 0M over data breach | Settlement invites criticism from lawmakers | Microsoft settles bribery case | Election security to take back seat at Mueller testimony MORE (D-Calif.) said Sunday that FBI Director James Comey's email to lawmakers regarding the Hillary ClintonHillary Diane Rodham Clinton5 things to know about Boris Johnson Trump says Omar will help him win Minnesota The Hill's Morning Report — Trump applauds two-year budget deal with 0 billion spending hike MORE email server investigation was "a terrible error in judgment."

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"I think this was a terrible error in judgment by the director, to release this kind of ambiguous letter. These may be pertinent; they may be significant; they may not be significant. They may not be pertinent," Schiff, the ranking member of the House Intelligence Committee, told ABC's "This Week."

On Friday, Comey sent a letter to Congress alerting lawmakers to the fact that the FBI discovered emails that may be relevant to the Democratic presidential nominee's server investigation.

It was later reported that the separate investigation was into former Rep. Anthony Weiner (D-N.Y.). Weiner is the husband of longtime Clinton aide Huma Abedin.

"That kind of an ambiguity bomb this close to an election was a terrible lapse in judgment," Schiff added.