The top Democrat on the US House Intelligence Committee has accused Republicans of tampering with a memo about FBI spying at the 2016 election.
Adam Schiff said Republicans had changed the text after it was voted on.
The secret document was passed by the Republican-dominated committee but needs approval from President Donald Trump to be made public.
It is believed to accuse the FBI of abusing its surveillance powers to target the Trump campaign.
Concerns about its contents were raised by the FBI itself which complained of “material omissions of fact that fundamentally impact the memo’s accuracy”.
Democrats fear the document may be an attempt to discredit the inquiry into Trump campaign links to Russia, which is being led by Sp
ecial Counsel Robert Mueller.
If Mr Trump gives his approval, the memo may be released later on Thursday.
The four-page document was compiled by staffers for House Intelligence Committee head Devin Nunes, a member of Mr Trump’s Republican party.
It apparently accuses the Department of Justice (DoJ) and the FBI (Federal Bureau of Investigation) of abusing a programme known as the Foreign Intelligence Surveillance Act (Fisa) during the presidential election campaign.
The allegation is that the FBI spied on a member of Mr Trump’s campaign on the basis of unproven accusations against Mr Trump known as the “Russian dossier”.
That dossier was compiled by former UK intelligence agent Christopher Steele with money financed in part from Hillary Clinton’s campaign.
Following his State of the Union speech on Tuesday night, Mr Trump was heard telling a Republican lawmaker he was “100%” for releasing the document.
According to Mr Schiff, the text approved by the committee on Monday is not the same as that given to the White House.
Mr Nunes sent a version of the memo that was “materially altered”, the Democrat said. He gave no details.
Quoted by Reuters news agency, a spokesman for Mr Nunes described the changes to the memo as minor, including two edits requested by the FBI and Democrats themselves.
Mr Schiff’s allegation was, the spokesman added, an “increasingly strange attempt to thwart publication”.
Source: BBC