The ranking Democrat on the House Intelligence Committee says Republicans substantially altered the classified memo about the origins of the FBI's Trump-Russia probe before they sent it to the White House.
Rep. Adam Schiff, D-Calif., said in an open letter that the changes were made without the knowledge of Democrats on the committee and that the committee's vote to release the memo was now invalid.
A spokesman for committee Chairman Devin Nunes, R-Calif., said the changes were "minor edits to the memo, including grammatical fixes and two edits requested by the FBI and by the minority themselves."
The House Intelligence Committee voted along party lines this week to approve releasing the memo, assembled by Nunes, to President Donald Trump and then to the public.
Trump has said he's "100 percent" in favor of releasing the document, and reports say the release could come as early as Thursday.
The FBI has said it has "grave concerns" about the accuracy of the top-secret memo. The memo reportedly focuses on the FBI's alleged use of a dossier compiled by former British spy Christopher Steele, who was paid by Democrats for his investigation of Trump's interactions with Russians.
In his letter Wednesday, Schiff said the version of the memo sent to the White House has been altered in "substantive" and "material" ways. He also noted that committee members "were never apprised of, never had the opportunity to review, and never approved."
The White House has not guaranteed that Trump will allow the memo to be released.
Read the statement the FBI sent CNBC below:
The FBI takes seriously its obligations to the FISA Court and its compliance with procedures overseen by career professionals in the Department of Justice and the FBI. We are committed to working with the appropriate oversight entities to ensure the continuing integrity of the FISA process.
With regard to the House Intelligence Committee's memorandum, the FBI was provided a limited opportunity to review this memo the day before the committee voted to release it. As expressed during our initial review, we have grave concerns about material omissions of fact that fundamentally impact the memo's accuracy.
—CNBC's Eamon Javers, Kevin Breuninger and The Associated Press contributed to this report.