Donald Trump attacks James Clapper after former Intel Chief says he was unfit to be President

Mr Clapper has become increasingly disillusioned with the President

Mr Clapper has become increasingly critical of Mr Trump (AP)

Donald Trump has launched an attack on a former intelligence chief who in recent days questioned his fitness for the presidency

James Clapper, who served as Director of National Intelligence under Barack Obama and stood down in January, has become increasingly critical of Mr Trump. Following the President's widely-criticised response to the neo-Nazi-led violence in Charlottesville that left a young woman dead, Mr Trump held a rally in Arizona where he defended his actions.

After the event, Mr Clapper said he had found Mr Trump’s speech in Phoenix to be “downright scary and disturbing”.

“I really question his ability to be - his fitness to be - in this office, and I also am beginning to wonder about his motivation for it,” he said on CNN. “How much longer does the country have to, to borrow a phrase, endure this nightmare?”

On Thursday, among a series of tweets, Mr Trump attacked Mr Clapper and accused him of lying to Congress.

“James Clapper, who famously got caught lying to congress, is now an authority on Donald Trump. Will he show you his beautiful letter to me,” he wrote.

Mr Clapper is a member of what Trump supporters have termed “the deep state”, the intelligence and law enforcement institutions they claim are opposed to the President.

There is little doubt that Mr Trump has become increasingly isolated among in his relationship with many such agencies. Last week, after Mr Trump appeared to defend those responsible for events in Charlottesville, four generals representing various branches of the armed services, tweeted to say there was no place for racism or bigotry in the military.

Mr Trump also saw senior business executives who made up two advisory councils quit, amid concern that his stance could hurt and offend not only their workforces but their customers. Members of an arts advisory group also resigned.