The director of the FBI has been accused of making a “huge blunder” in his handling of the investigation into Hillary Clinton’s emails.
In a letter made public on Friday, FBI director James Comey revealed the bureau would examine whether newly discovered emails contained sensitive government information.
Matthew Miller, a former chief spokesman for the US Department of Justice, told Sky News: “The Director of the FBI has made a huge blunder here that has troubling consequences for how he handles his job and for our democracy.
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“There are rules in place that really are supposed to limit how the FBI handles these types of situations and they are not supposed to make these types of public statements so close to an election, especially when there is no evidence at all that we know of that anyone did anything wrong.”
The FBI had concluded in July that Mrs Clinton was “extremely careless” in handling classified information while Secretary of State, with scores of emails on her private server containing highly classified information.
But the bureau did not recommend criminal charges.
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Mr Miller said: “(Mr Comey) didn’t actually provide any information to the public – all he said is that they’re reviewing something new.
“But voters are left to look at this – they don’t know what to make of this, they have no idea what it is they’re looking at.
“He has created a situation where Republicans can hurl innuendo with no basis in fact and there’s no way for Hillary Clinton to defend herself.”
He added: “If he did feel compelled (to investigate), he should have done it how the FBI handles every other case – quietly investigated, not commented on it.
“If he did feel obligated to inform Congress of what he was doing, wait until after the election to do so, rather than turn the FBI’s investigation into a political football 10 days before the election.”
Jesse Byrnes, editor of political website The Hill, told Sky News that Mr Comey’s announcement was “one of the almost worst nightmare scenarios for the Clinton campaign”.
He added: “The timing…was an October surprise if we’ve ever seen one.”
Responding at a hastily arranged news conference, Mrs Clinton demanded the FBI disclose full details of its new probe, which came to light just 11 days before the election.
“The American people deserve to get the full and complete facts immediately,” Mrs Clinton told reporters in Iowa.
“It’s imperative that the bureau explains this issue in question, whatever it is, without any delay.”
Speaking from the campaign trail in Daytona Beach, Florida, on Saturday, she called the FBI’s actions “unprecedented” and “troubling”.
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The messages were discovered after the FBI seized four electronic devices belonging to Mrs Clinton’s aide Huma Abedin and her husband Anthony Weiner, the New York Times reported.
They were taken during an investigation into illicit text messages between the former Congressman and a 15-year-old girl.
An unnamed US official told Associated Press the new emails did not come from Mrs Clinton’s private server.
The news prompted a gleeful response from Mrs Clinton’s Republican rival Donald Trump, who told his supporters the development is “bigger than Watergate”.
At a rally in New Hampshire, Mr Trump said: “Hillary Clinton’s corruption is on a scale we have never seen. We must not let her take her criminal scheme into the Oval Office.”
:: Watch America Decides, a special programme on the US election at midnight on Monday.