American President Donald Trump took to Twitter on Sunday to unload on James Comey over his forthcoming memoir, calling him “slippery”, suggesting he should be in jail and labelling him “the WORST FBI Director in history, by far!” The president fired off a series of tweets ahead of Mr Comey’s first interview on the book, which offers his version of the events surrounding his firing as FBI director and the investigations into Russian election meddling and Hillary Clinton’s email practices. The interview will be aired on Sunday night on ABC. In an excerpt shown on Saturday, Mr Comey said his belief that Mrs Clinton would beat Mr Trump in the 2016 presidential election was a factor in his decision to disclose the investigation into her emails. Mr Trump seized on that, saying Mr Comey “was making decisions based on the fact that he thought she was going to win, and he wanted a job. Slimeball!” Mr Comey's disclosure shortly before the election that the FBI had reopened its investigation into her email use enraged Democrats. After Mrs Clinton's loss, many Democrats blamed Mr Comey, and she has said it hurt her election prospects. _______________ Read more: _______________ The president on Sunday again pushed back against Mr Comey's claims that he sought his loyalty, saying: "I hardly even knew this guy. Just another of his many lies." He also suggested Mr Comey should be imprisoned, saying, “how come he gave up Classified Information (jail), why did he lie to Congress (jail)?” There is no indication Mr Comey is under investigation for doing either. Asked if the president wanted the justice department to investigate Mr Comey, White House spokeswoman Sarah Huckabee Sanders said on Sunday on ABC's <em>This Week</em> that she was not aware of a specific request, but said: "If they feel there was any wrongdoing, they should certainly look into that just as they do on a number of other topics." Mr Comey is embarking on a public roll-out of his book, <em>A Higher Loyalty</em>, which is published on Tuesday. In the book, he compares Mr Trump to a mafia don and calls his leadership of the country "ego driven and about personal loyalty". Mr Trump fired the FBI director in May last year, setting off a scramble at the justice department that led to the appointment of Robert Mueller as special counsel overseeing the Russia investigation. Mr Mueller's probe has expanded to include whether the president obstructed justice by firing Mr Comey. The president has said he fired Mr Comey because of his handling of the FBI’s investigation into Clinton’s email practices. Mr Trump used the investigation as a cudgel in the campaign and repeatedly said Mrs Clinton should be jailed for using a personal email system while serving as secretary of state. Democrats, on the other hand, have accused Mr Comey of politicising the investigation. In the interview excerpt released on Saturday, Mr Comey said he did not remember “consciously thinking” about the election results as he decided to disclose that the FBI had reopened its investigation into candidate Clinton’s email use. But he acknowledged: “I was operating in a world where Hillary Clinton was going to beat Donald Trump, and so I’m sure that it was a factor.” He added: “I don’t remember spelling it out, but it had to have been that she’s going to be elected president, and if I hide this from the American people, she’ll be illegitimate the moment she’s elected, the moment this comes out.” The Republican National Committee has helped with the push-back effort against Mr Comey and his book by launching a website and supplying surrogates with talking points that question his credibility. On Sunday, before the ABC interview aired, Mr Comey tweeted that his book draws on stories from his life and from lessons he has learnt from others. “3 presidents are in my book: 2 help illustrate the values at the heart of ethical leadership; 1 serves as a counterpoint,” he wrote. “I hope folks read the whole thing and find it useful.”