Trump hits bact at Comey

US President Donald Trump has attacked, via a tweet, the former FBI Director James Comey's comments of likening him to being a 'mafia boss'.

President Trump says, 'he is weak and untruthful slime ball who was, as time has proven, a terrible Director of the FBI.'

James Comey has written an explosive new book which is set to go on sale next Tuesday.

Comey was fired by Trump in May last year. In his memoir he accuses him of trying to involve intelligence officers in his own political battles, saying the President is untethered to truth and ego driven.

"I found myself having flashbacks to my earlier career as a prosecutor against the Mob," he said. "The silent circle of assent. The boss in complete control. The loyalty oaths. The us-versus-them world view. The lying about all things, large and small."

Comey says he regrets the way he communicated on the FBI investigation into Hillary Clinton's email management during the 2016 Presidential election.

Comey oversaw the investigation into the mishandling of classified government secrets by her and her staff on the email server kept in her New York home.

Jonathan Lemire White House Reporter said, "He sort of spent a lot of time really sort of criticizing the Secretary, only at the end to say 'but we're not finding any charges against her. He wishes he could have done that differently."

But he maintains he had no choice other than to make the information public.

At the time of his firing last May, Comey was overseeing a counterintelligence investigation into possible Russian government efforts to influence the US election.