Former FBI director James Comey has mocked the memo released by Republicans after being declassified by US President Donald Trump, saying it amounts to very little.

“That’s it?” Mr Comey posted to Twitter on Friday (US time).

“Dishonest and misleading memo wrecked the House intel committee, destroyed trust with Intelligence Community, damaged relationship with FISA court, and inexcusably exposed classified investigation of an American citizen. For what?” Mr Comey wrote, adding: “DOJ [Department of Justice] & FBI must keep doing their jobs.”

That’s it? Dishonest and misleading memo wrecked the House intel committee, destroyed trust with Intelligence Community, damaged relationship with FISA court, and inexcusably exposed classified investigation of an American citizen. For what? DOJ & FBI must keep doing their jobs.

— James Comey (@Comey) February 2, 2018

The tweet was the latest in a series from Mr Comey this week as Mr Trump clashed with the FBI over the explosive release of the GOP-written memo.

Republicans on Friday (US time) released the Nunes memo, a document they say reveals a so-called “deep state” bias against Mr Trump and abuse of the government’s surveillance powers.

The memo — named for its author Devin Nunes, the GOP chairman of the House Intelligence Committee — was criticised by the FBI for being misleading.

FBI director Christopher Wray, cautioned against its release.

The FBI said that it had “grave concerns about material omissions of fact that fundamentally impact the memo’s accuracy”.

“I stand by our shared determination to do our work independently and by the book,” Mr Wray said in a statement to FBI staff, parts of which were reported by Reuters.

“Talk is cheap. The work you do is what will endure,” he reportedly wrote.

What is the memo and why does it matter?

The memo largely focuses on the way the FBI and the Justice Department obtained surveillance warrants, starting on October 21, 2016, to monitor Carter Page, a volunteer Trump campaign adviser, and how the law enforcement agency then obtained three renewals from the Foreign Intelligence Surveillance Act court.

Mr Trump and congressional Republicans have for some time been attacking the FBI for its investigation of potential ties between Russia and Mr Trump’s 2016 campaign.

Mr Trump and Republicans on the House intelligence committee ramped up those attacks with the publication of the GOP-authored memo.

The FBI, Justice Department and Democrats lobbied Mr Trump to stop the release, saying it could harm national security and mislead the public.

The memo claimed that an “essential part” of the FBI’s application was a dossier compiled by Christopher Steele, an ex-British intelligence officer, on the extent of Mr Trump and his campaign’s contacts with the Russians.

“Steele was a longtime FBI source who was paid over $160,000 by the DNC and Clinton campaign, via the law firm Perkins Cole and the research firm Fusion GPS, to obtain derogatory information about Donald Trump’s ties to Russia,” the memo says.

It noted that Mr Steele “was suspended then terminated as an FBI source for what the FBI defines as the most serious of violations — an unauthorised disclosure to the media of his relationship with the FBI in an October 30, 2016 Mother Jones article by David Corn”.

The Nunes memo does not go into detail on what other factors the FBI and the DOJ used in their application to justify the issue of a warrant, but tries to make the case that FBI and DOJ officials held a bias against Mr Trump.

Mr Trump ordered it declassified, writing in a tweet on Friday morning: “The top Leadership and Investigators of the FBI and the Justice Department have politicized the sacred investigative process in favor of Democrats and against Republicans — something which would have been unthinkable just a short time ago. Rank & File are great people!”

The top Leadership and Investigators of the FBI and the Justice Department have politicized the sacred investigative process in favor of Democrats and against Republicans – something which would have been unthinkable just a short time ago. Rank & File are great people!

— Donald J. Trump (@realDonaldTrump) February 2, 2018

‘No evidence of collusion’

Congressman Nunes said on Friday (US time) there was “no evidence of collusion” between Mr Trump and Russia.

He told Fox News that Attorney General Jeff Sessions, Deputy Attorney General Rod Rosenstein and FBI Director Mr Wray “have work to do”, but did not say if they would be fired.

Democrats say the four-page memo mischaracterises highly sensitive classified information and is intended to undermine Special Counsel Robert Mueller’s investigation into the Russia matter launched in May 2017, which grew from an earlier FBI probe.

Two White House officials on Friday said Mr Trump was not considering firing Mr Rosenstein, although Mr Trump declined to express confidence in the Justice Department’s second-in-command who had objected to the memo’s release.

Mr Rosenstein is overseeing the Mueller probe and has been a growing target for the President’s frustration as the investigation continues.

The Democrats, led by Adam Schiff, called it a “shameful effort to discredit” the FBI, the Justice Department and a federal investigation into Russian meddling in the 2016 election.

The President’s decision to publicly release a misleading memo attacking DOJ & FBI is a transparent attempt to discredit these institutions and undermine Mueller’s probe.

We'll fight to release our classified response. Until then here's a glimpse at what's wrong with their memo: pic.twitter.com/HX0J6UtDLY

— Adam Schiff (@RepAdamSchiff) February 2, 2018

The Democrats said they hoped to release their own memo responding to the allegations on February 5.

—with AAP