White House Press Secretary Sean Spicer said in a statement that Mr Comey has been "terminated and removed from office." Mr Trump was said to have acted on "clear recommendations" from Attorney General Jeff Sessions and Deputy Attorney General Rod Rosenstein, in a move that has shocked Washington.
However, Democratic Senators were quick to point out the constitutional crisis that has been created by Mr Trump removing a man in charge of investigating him. Senator Dick Durbin said on the Senate floor that the firing of Mr Comey raises questions "as to whether the Russian interference in the last presidential election... will also be investigated by the FBI."
Mr Durbin called on the White House to clarify whether the investigation will continue, adding that any "attempt to stop or undermine the FBI probe would raise grave constitutional issues".
Mr Trump's statement indicated that a search for a new director of the FBI "will begin immediately."
In Mr Trump's letter formally informing Mr Comey of his termination, he was appreciative of Mr Comey "informing [him] on three separate occasions" that the president was not under investigation by the agency.
However, Mr Trump "concur[s] with the judgement of the Department of Justice (DOJ) that you are not able to effectively lead the Bureau."
"It is essential we find new leadership...that restores public trust and confidence," Mr Trump said.
In addition to the Senate and FBI investigations, the House Intelligence Committee is also conducting one. Democratic Representative Eric Swallwell, the ranking member on the committee, said that Mr Comey's firing "should send a chill down the spine of every American, no matter who they voted for."
“The administration of justice must remain free of political influence, and President Trump has just leaped over that line," Mr Swalwell said.
Calls from several members of Congress, including Republican Senator John McCain, about having an independent, bipartisan commission to conduct the Russia investigation have been amplified in the wake of Mr Comey's dismissal.
The controversial orders Donald Trump has already issued
The controversial orders Donald Trump has already issued
1/9 Trump and the media
White House Press Secretary Sean Spicer takes questions during the daily press briefing
2/9 Trump and the Trans-Pacific Partnership
Union leaders applaud US President Donald Trump for signing an executive order withdrawing the US from the Trans-Pacific Partnership negotiations during a meeting in the Roosevelt Room of the White House in Washington DC. Mr Trump issued a presidential memorandum in January announcing that the US would withdraw from the trade deal
3/9 Trump and the Mexico wall
A US Border Patrol vehicle sits waiting for illegal immigrants at a fence opening near the US-Mexico border near McAllen, Texas. The number of incoming immigrants has surged ahead of the upcoming Presidential inauguration of Donald Trump, who has pledged to build a wall along the US-Mexico border. A signature campaign promise, Mr Trump outlined his intention to build a border wall on the US-Mexico border days after taking office
4/9 Trump and abortion
US President Donald Trump signs an executive order as Chief of Staff Reince Priebus looks on in the Oval Office of the White House. Mr Trump reinstated a ban on American financial aide being granted to non-governmental organizations that provide abortion counseling, provide abortion referrals, or advocate for abortion access outside of the United States
5/9 Trump and the Dakota Access pipeline
Opponents of the Keystone XL and Dakota Access pipelines hold a rally as they protest US President Donald Trump's executive orders advancing their construction, at Columbus Circle in New York. US President Donald Trump signed executive orders reviving the construction of two controversial oil pipelines, but said the projects would be subject to renegotiation
6/9 Trump and 'Obamacare'
Nancy Pelosi who is the minority leader of the House of Representatives speaks beside House Democrats at an event to protect the Affordable Care Act in Los Angeles, California. US President Donald Trump's effort to make good on his campaign promise to repeal and replace the healthcare law failed when Republicans failed to get enough votes. Mr Trump has promised to revisit the matter
7/9 Donald Trump and 'sanctuary cities'
US President Donald Trump signed an executive order in January threatening to pull funding for so-called "sanctuary cities" if they do not comply with federal immigration law
8/9 Trump and the travel ban
US President Donald Trump has attempted twice to restrict travel into the United States from several predominantly Muslim countries. The first attempt, in February, was met with swift opposition from protesters who flocked to airports around the country. That travel ban was later blocked by the Ninth Circuit Court of Appeals. The second ban was blocked by a federal judge a day before it was scheduled to be implemented in mid-March
SANDY HUFFAKER/AFP/Getty Images
9/9 Trump and climate change
US President Donald Trump sought to dismantle several of his predecessor's actions on climate change in March. His order instructed the Environmental Protection Agency to reevaluate the Clean Power Plan, which would cap power plant emissions
Mr McCain expressed his "disappointment" in Mr Trump's decision, calling Mr Comey a "man of honor and integrity" in a statement.
Several Democrats have also called the firing “Nixonian," referring to the Saturday Night Massacre – when former President Richard Nixon dismissed Archibald Cox, the special prosecutor in the Watergate scandal. That night, the attorney general and deputy attorney general resigned in protest to the firing of Mr Cox.
"Today's action by President Trump completely obliterates any semblance of an independent investigation into Russian efforts to influence our election, and places our nation on the verge of a constitutional crisis," said Representative John Conyers, senior Democrat on the House Judiciary Committee.
Mr Conyers and other Democrats have echoed Mr McCain's calls for an independent commission or a special prosecutor to investigate Russian influence in the 2016 election - with Chuck Shumer, the top-ranking Democrat in the Senate calling for a "fearless" special prosecutor to take on the Trump-Russia probe, wondering whether the firing of Mr Comey meant the various Russia probes were "getting too close to home for the President".
News that Mr Comey made inaccurate statements to the Senate, while under oath, surfaced recently and could also point to another possible reason for his dismissal.
Mr Comey made headlines in July 2016 with a letter to Congress detailing the end of the FBI investigation into Hillary Clinton's use of a private server to send classified emails while she was serving as Secretary of State. A further letter in October of that year - mere days before the presidential election -said further emails would be investigated, while accusing her top aide, Huma Abedin, of sending classified information in a similar manner.
Mr Comey said in front of the Senate Intelligence Committee last week that Ms Abedin “forwarded hundreds and thousands of emails” that contained classified information to the laptop of husband and erstwhile Congressman Anthony Weiner.
On Tuesday, the FBI said in a two-page letter to the Senate Judiciary Committee that only “a small number” of the thousands of emails found on the laptop had been forwarded there while most had simply been backed up from electronic devices. Most of the email chains on the laptop containing classified information were not the result of forwarding, the FBI said.
Donald Trump's first 100 days: in cartoons
Donald Trump's first 100 days: in cartoons
Donald Trump's first 100 days in office were marred by a string of scandals, many of which caught the eye of the Independent's cartoonists
Trump's first 100 days have seen him aggressively ramp up tensions with his nuclear rivals in North Korea
Mr Trump has warned of a "major, major conflict" with the pariah nation lead by Kim Jong Un
Mr Trump dropped the "mother of all bombs" on alleged ISIS-linked militants in Afghanistan, amid an escalation of US military intervention around the globe
Mr Trump has been accused of falling short of the standards set by his predecessors in the Oval Office, including Franklin D Roosevelt
The tycoon's ascension to the White House came at a time when the balance of power is shifting away from Western nations like those in the G7 group
Western politicians, including the British Conservative party, have been accused of falling in line behind Mr Trump's proposals
Brexit is seen to have weakened Britain, reducing still further any political will to resist American leadership
Mr Trump's leadership has been marked by sudden and unexpected shifts in global policy
Trump's controversial missile strike on Syria, which killed several citizens, was seen by some analysts as an attempt to distract from his policy elsewhere
The President has also spent a large majority of his weekends golfing, rather than attending to matters of state
Though free of gaffes, a visit from Chinese president Xi Jinping spotlighted trade tensions between the two states
One major and unexpected setback came when Mr Trump's Healthcare Bill was struck down by members of his own party
Mr Trump has been a figure of fun in the media, with his approval at record lows
A string of revelations about Mr Trump's financial indiscretions did not mar his surge to the White House
Outgoing President Barack Obama was accused of wiretapping Trump Tower by his successor in America's highest office
The alleged involvement of Russian intelligence operatives in securing Mr Trump the presidency prompted harsh criticism
The explosive resignation of Security Adviser Michael Flynn, who lied about his links to the Russian ambassador, was just one scandal to hit the President
Many scandals, such as the accusation Barack Obama was implicated in phone-hacking, first broke on Mr Trump's Twitter feed
Donald Trump's election provoked mass protests in the UK, with millions signing a petition to ban him from the country
Donald Trump cited a non-existent terror attack in Sweden during a campaign rally
Donald Trump stands accused of stoking regional tensions in Eastern Asia
North Korea has launched a number of failed nuclear tests since Mr Trump took power
Theresa May formally rejected the petition calling for Mr Trump to be banned from the UK
When Mr Trump's initial so-called Muslim ban was struck down by a federal justice, the President mocked the 69-year-old as a "ridiculous", "so-called judge"
A week after his inauguration, Theresa May met with Mr Trump at the White House
Donald Trump's first days in office were marked by a hasty attempt to follow through on many of his campaign promises, including the so-called Muslim ban
Donald Trump's decision to ban citizens of many majority-Muslim countries from the US sparked mass protests
Revelations about Donald Trump's sexual improprieties were not enough to keep him from being elected President
British PM Theresa May was criticised by many in the press for cosying up to the new President
One of Mr Trump's top aides, Kelly Anne Conway, was mocked for describing mistruths as "alternative facts"
British PM Theresa May was quick to demonstrate that her political aims did not hugely differ from Mr Trump's
Donald Trump's inauguration, on 20 January 2017, sparked protests both at home and abroad
Robert Cattanach, a partner specialising in cybersecurity at the law firm Dorsey & Whitney and a former trial lawyer at the DOJ, told The Independent that perjury is “tough to prove."
“It requires a knowing misstatement of fact,” he said.
Mr Cattanach said any letter sent by the FBI to correct the record would have needed to explain “why [Mr Comey] said what he said,” because if it was just an honest mistake Mr Comey did not actual commit perjury in the legal sense.
There is no apparent language in the FBI letter indicating why Mr Comey made the error in his testimony on Ms Abedin's email.
In his memo to the Attorney General about the dismissal, Mr Rosenstein called the way Mr Comey handled the entire Clinton email investigation "wrong."
He wrote that Mr Comey undermined the agency and entire DOJ when he said he had to make a decision whether to "speak" about the Clinton email investigation or "conceal" it.
"When federal agents and prosecutors quietly open a criminal investigation, we are not concealing anything," Mr Rosenstein wrote. It has been a longstanding policy of the DOJ not to publicly comment on investigations with "non-public" information.
Mr Cattanach said that "if Comey had not promised Congress that he would ‘get back to them if anything changed’ he would almost certainly have been safe in relying on standard FBI policy." Instead Mr Comey put himself in a "lose-lose" situation, following the letter sent in July and that led to the second letter in October that said a number of further emails from Ms Clinton would be investigated.
In his testimony on 3 May, Mr Comey said knowing he had an impact on the US election because he spoke about the Clinton investigation and not the one regarding Russian ties to the Trump team, made him "nauseous."Reuse content