Filmmaker Michael Moore has called on the Democratic Party in America to declare a national emergency, following the revelation that Donald Trump and his staff are being investigated by the FBI.

FBI director James Comey confirmed this week that investigators are looking at alleged interference by Russia in the 2016 election, and any possible ties between Russia and Mr Trump’s campaign team.

Writing on Instagram, Mr Moore has called for all business with Mr Trump to be halted, including decisions on legislation and confirmation of nominees to positions of public office, while he is under investigation.

“The Democratic Party needs to declare a National Emergency. For the first time in our history, the President of the United States and his staff are under investigation for espionage,” Mr Moore claims in the post.

“This announcement, by the head of the Trump-friendly FBI, is a shock to our democracy. The Democratic leadership in the House and Senate needs to bring a halt to all business being done in the name of this potential felony suspect, Donald J. Trump.

“No bill he supports, no Supreme Court nominee he has named, can be decided while he is under a criminal investigation. His presidency has no legitimacy until the FBI - and an independent investigative committee - discovers the truth. Fellow citizens, demand the Democrats cease all business.”

Mr Trump’s Supreme Court nominee, Neil Gorsuch, is this week attending confirmation hearings on his position.

Mr Moore, who is known for documentaries Bowling for Columbine and Fahrenheit 9/11’, ended his post on a quote from President Richard Nixon: "The American people have a right to know if their President is a crook.” The famous quote comes from a 1973 televised question and answer session with the press, when Mr Nixon was being probed about his tax payments. He denied any involvement in the Watergate scandal in the same session.

Mr Trump has denied any links between the Russian government and his campaign team.

The FBI probe has been on-going since July last year but its existence was confirmed this week in a rare move by the agency. After outlining the nature of the counterintelligence effort, Mr Comey said on Monday: “I cannot say more about what we are doing and whose conduct we are examining.”