Explainer: Everything you need to know about the explosive secret FBI memo
The FBI secured a warrant to wiretap an official with Donald Trump's presidential campaign by repeatedly concealing from a special court that they were relying on information paid for by Democrats, according to an explosive declassified memo.
What is contained in the memo?
It suggested the bureau and Department of Justice relied heavily on a dossier provided by former British intelligence officer Christopher Steele without revealing to the court that he had ultimately been funded by the Democratic National Committee and the Clinton campaign.
The three-and-a-half page memo was written by Republicans on the House intelligence committee based on what they have learned in an investigation. It was released publicly after being declassified by Mr Trump.
Devin Nunes, the Republican chairman of the committee, said it showed "serious violations of the public trust" by intelligence and law enforcement agencies.
Why did the FBI issue a warrant to wiretap a Trump advisor?
According to the memo on October 21, 2016 a warrant was sought and obtained for electronic surveillance of Carter Page, a volunteer adviser to the Trump campaign who had traveled to Russia.
The warrant was sought under the Foreign Intelligence Surveillance Act (FISA). Such warrants have to be renewed in a secret court every 90 days. Each time there has to be a "probable cause" shown, and submissions to the court are classified.
The memo said the integrity of the process, and public trust in it, was "necessarily dependent on the government's production to the court of all material and relevant facts".
But it said: "In the case of Carter Page the government had at least four independent opportunities before the FISA court" but "material and relevant information was omitted".
It said the dossier provided by Mr Steele had formed an "essential part" of the warrant application.
Why is the memo so controversial?
Mr Steele, a longtime FBI source, had been paid over $160,000 by the Democratic National Committee and the Clinton campaign".
Payments were via the law firm Perkins Coie and opposition research firm Fusion GPS "to obtain derogatory information on Donald Trump's ties to Russia," the memo said.
It said neither the original application, nor any of the 90-day renewals, disclosed the role of the DNC or Clinton campaign "even though the origins of the Steele dossier were then known to senior Department of Justice and FBI officials".
The memo said: "The application does not mention Steele was ultimately working on behalf of - and paid by - the DNC and Clinton campaign."
In its application to the FISA court the FBI had also cited extensively from a Yahoo News article of September 23, 2016 about Page's trip to Moscow.
The memo said: "This article does not corroborate the Steele dossier because it is derived from information leaked by Steele himself to Yahoo News.
"Steele has admitted in British court filings that he met with Yahoo News - and several other outlets."
The memo said Mr Steele was "suspended and then terminated" as an FBI source for "the most serious of violations" - unauthorised disclosure of his relationship with the FBI to the media.
This demonstrated that Mr Steele had "become a less than reliable source for the FBI" but the Department of Justice still maintained contact with him.
Mr Steele's contact was Deputy Attorney General Bruce Ohr whose wife worked for Fusion GPS "assisting with the cultivation of opposition research against Trump paid for by the DNC and Clinton campaign".
The Ohrs relationship with Mr Steele and Fusion GPS was "inexplicably concealed" from the FISA court, the memo said.
It suggested that after Steele was terminated as an FBI source his information was only "minimally corroborated" yet it was still used for warrants against Page.
"While the court application relied on Steele's previous record of credible reporting on other unrelated matters it ignored or concealed his anti-Trump financial and ideological motivations," the memo said.
Democrats on the House Intelligence Committee called the release of the memo a "shameful effort to discredit" the FBI, the Department of Justice, and the ongoing investigation by special counsel Robert Mueller into Russian meddling in the 2016 election.
Why did Republicans want it released?
Republicans argued the memo needed to be published because it raised questions about how officials secured a wiretap on a US citizen.
They dismissed claims about their motives by saying it was entirely right for the House intelligence committee to raise such concerns.
However Democrats accused the Republicans of a “shameful effort” to “discredit” the intelligence services by painting a partial picture and are threatening to produce their own memo.
They also claimed the real reason Republicans want the memo out is because helps undermine Robert Mueller's investigation into Russian election meddling.
If voters have more doubts about intelligence and justice officials then they are less likely to believe whatever Mr Mueller, the special counsel, eventually finds out.
In a statement the Democrats said: "The selective release and politicisation of classified information sets a terrible precedent and will do long-term damage to the intelligence community and our law enforcement agencies."
The release also set up an extraordinary confrontation between Republicans and the leadership of the FBI, which had pre-emptively issued a statement saying they had "grave concerns" about the memo.
Christopher Wray, the FBI Director, was said to have "raised hell" in advance of the release and there was speculation he could resign.