Donald Trump could be impeached under the 25th Amendment of the US Constitution following his alleged sharing of classified information with the Russians, according to a top lawyer.

Richard Painter, former ethics lawyer for George W Bush, tweeted that "any other President would have been out of there within 48 hours" for distributing the information from a US ally without their permission.

“Cabinet and VP need to read Amendment 25,” Mr Painter added.

Under section four of the 25th Amendment, a President can be removed if deemed “unable to discharge the powers and duties of his office”.

Although the amendment was designed to cover illness and death, such as in the cases of former Presidents John F Kennedy and Ronald Reagan, the wording could be interpreted to cover other inabilities to carry out Presidential duties.

Mr Painter’s assessment follows reports that Mr Trump said he had an “absolute right” to discuss sensitive information with Russian ambassador Sergei Kislyak and Russian foreign minister Sergei Lavrov last week.

"As President I wanted to share with Russia (at an openly scheduled W.H. meeting) which I have the absolute right to do, facts pertaining to terrorism and airline flight safety," the President wrote.

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"Humanitarian reasons, plus I want Russia to greatly step up their fight against [IS] & terrorism."

Mr Trump’s alleged disclosure is not illegal, but will be seen as a potential act of incompetence by his critics and a breach of trust within the intelligence community.

His national security adviser, H R McMaster, denied that his boss had shared classified information without authorisation, and said Mr Trump was “not even aware” of the source and method of obtaining information about an Isis plot to use laptops to bring down planes.

Mr Trump was reported to have discussed the information to the extent that the Russians could have worked out who the source was, however, potentially putting informants’ lives at risk.

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A new poll from Public Policy Polling found that more Americans support Mr Trump’s impeachment than oppose it, for the first time.

Under Amendment 25, however, the task would fall to Vice President Mike Pence and House Speaker Paul Ryan to make a written assertion that the President was unable to continue in the White House - an unlikely scenario.

Mr Trump’s meeting with the Russians, which barred US journalists and did not produce a transcript of the discussion, follows his firing of former FBI director James Comey while Mr Comey was investigating the President’s and his team’s alleged links to Russia before and after the campaign.

After the meeting with the two Russian officials, other attendees realised Mr Trump’s alleged mistake and informed the Central Intelligence Agency and the National Security Agency, who had to tell the US ally about the slip-up.

"If I had told White House staff 'don’t leak classified information to the Russians' they would have laughed," Mr Painter tweeted.

He added that the UK and other US allies would be "nuts" to continue sharing sensitive material with Mr Trump.

Security adviser Mr McMaster defended Mr Trump to reporters.