Allegations Donald Trump revealed highly classified information to Russian officials are "the most serious charge ever made against a sitting president", former Harvard law professor Alan Dershowitz has said.
The legal scholar said people should not minimise the gravity of claims the President revealed the top-secret information about Isis to the Russian foreign minister and ambassador at a White House meeting.
The information is said to have been provided to Mr Trump by an American ally through a sensitive intelligence sharing arrangement, reported The Washington Post.
"This is the most serious charge ever made against a sitting president. Let’s not minimize it. Comey affair now in the wastebasket of history," wrote the professor on Twitter.
Professor Dershowitz, 78, spent more than 50 years at Harvard, becoming the college's youngest ever professor of law in 1967 at the age of 28.
According to the Post, the source of the information had not given permission for the information to be shared with Russia.
After the meeting, White House officials took steps to contain the damage, placing calls to the CIA and National Security Agency. It has not been reported which third country was involved.
The British Embassy in Washington declined to comment when contacted by The Independent.
The White House has denied that the President leaked the classified information to Sergei LAvrov and Ambassador Sergey Kislyak.
In a brief appearance outside the White House, HR McMaster, the president's national security advisor, said: “The story that came out tonight, as reported, is false."
“At no time were intelligence sources or methods discussed,” Mr McMaster said. “And the president did not disclose any military operations that were not already publicly known.
"Two other senior officials who were present, including the Secretary of State, remembered the meeting the same way and said so. The on-the-record accounts should outweigh those of anonymous sources.”
He said he had been present at the meeting.
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
The development was the latest incident to shake Washington, still stunned by the firing of FBI Director James Comey. The White House has been scrambling to project a sense of order, after Mr Trump himself created mayhem by contradicting his own officials explanation for the firing.
The report on Monday evening said one the most concerning aspects of the slip, was that Mr Trump revealed the city in Isis territory where the US intelligence partner detected the threat.
There were claims that Russia could use the information to undermine the US, or its ally.Reuse content