The FBI says it has 'grave concerns' about a secret memo which the White House is considering releasing to the public.

Republican lawmakers have been pushing for the release of the memo, which was prepared by the office of House Intelligence Committee chairman Devin Nunes.

According to The Washington Post, the memo is said to raise concerns about the surveillance of former Trump campaign adviser Carter Page.

The memo is believed to allege that the FBI and Justice Department overstepped their authority to obtain a Foreign Intelligence Surveillance Court (FISA) warrant, and reportedly suggests the agencies relied on claims within a controversial and unverified dossier prepared on Donald Trump and Russia.

Republicans on the House Intelligence Committee have voted to release the memo, with President Trump having final authority over its release.

A decision is expected shortly once the document is fully scrutinised by White House lawyers, with President Trump's Chief of Staff John Kelly having indicated that he expected it to be released "pretty quick".

The Washington Post yesterday reported that Deputy Attorney General Rod J Rosenstein had urged White House officials to not release the document over fears it could jeopardise classified information.

"Grave concerns"

The FBI, meanwhile, has moved to publicly dispute the contents of the memo.

In a statement, the FBI said: "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."

Adan Schiff, the senior Democrat on the House Intelligence Committee, has claimed: "The decision by Nunes to employ an obscure rule to release classified information for partisan political purposes crossed a dangerous line, and increases the risk of a constitutional crisis."

He suggested the decision is a result of "growing alarm" among Republicans over special counsel Robert Mueller's ongoing investigation into alleged Russian interference in the 2016 campaign.

He also argued that Mr Nunes "made material changes to the memo he sent to White House - changes not approved by the Committee".

BREAKING: Discovered late tonight that Chairman Nunes made material changes to the memo he sent to White House – changes not approved by the Committee. White House therefore reviewing a document the Committee has not approved for release. pic.twitter.com/llhQK9L7l6

— Adam Schiff (@RepAdamSchiff) February 1, 2018

Meanwhile, Mr Nunes himself accused the FBI and Departmet of Justice of making "spurious objections" to the memo's release.

He said: "It’s clear that top officials used unverified information in a court document to fuel a counter-intelligence investigation during an American political campaign.

"Once the truth gets out, we can begin taking steps to ensure our intelligence agencies and courts are never misused like this again."