FBI Director James Comey has defended his handling of the Hillary Clinton email investigation, saying it was consistent with his management of a probe into alleged Russian meddling in the 2016 US election and links between Moscow and the Trump campaign.

During a Senate Judiciary Committee hearing, Mr Comey said that it made him “mildly nauseous” to think that his decision to disclose an investigation into Ms Clinton’s use of a private email server may have impacted the election, but that he stood by his choice.

He added that he could not consider “for a second whose political fortunes will be affected” by revealing an investigation.

Mr Comey sent a letter on 28 October to congressional leaders saying the FBI would continue investigating whether Ms Clinton sent additional classified emails from a private email server while she was Secretary of State. In July, he had recommended that no charges be filed against Ms Clinton or her aides, effectively closing the email probe.

During the hearing on Wednesday, Mr Comey said his investigative team informed him on 27 October that there appeared to be thousands of Ms Clinton’s emails on the laptop of Anthony Weiner – the disgraced husband of one of her top aides Huma Abedin – including what they thought might be the missing emails from her first three months as Secretary of State.

“We never found any emails from her first three months,” Mr Comey said. “She was using a Verizon Blackberry then, and that’s obviously very important because if there was evidence that she was acting with bad intent, that’s where it would be.”

On the morning of 28 October, Mr Comey said he had to either conceal the information or ‘speak’.

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Mr Comey said that informing Congress of the restart of the investigation would “be really bad”, as the election was 11 days away. On the other hand, “concealing in my view would be catastrophic”, he said. “Not just to the FBI, but well beyond. Between really bad and catastrophic, I said we’ve got to walk into the world of really bad.”

“Even in hindsight – and this has been one of the world’s most painful experiences – I would make the same decision,” Mr Comey added.

Democratic senator Sheldon Whitehouse told Mr Comey that he did “not doubt [his] honesty “for a minute”, but that he does think there were significant mistakes made in the handling of the email case.

Before the House of Representatives' Intelligence Committee in March, Mr Comey said that over the summer the FBI had opened a probe into alleged Russian meddling in the presidential election and whether the Trump campaign was involved. The disclosure elicited further criticism from Democrats during the hearing, who questioned why Mr Comey had not confirmed the existence of the investigation earlier.

“I think I treated both investigations consistently under the same principals,” Mr Comey responded. “People forget we would not confirm the existence of the Hillary Clinton email investigation until three months after it began, even though it began with a public referral and the candidate herself talked about it.”

“In October of 2015, we confirmed it existed, and then said not another word, not a peep about it until we were finished,” he added. Because the investigation into Trump officials’ connection with Russia began much later, Mr Comey was not in a position to confirm the inquiry.

The FBI’s director has said he will not “say another peep” on the ongoing investigation into alleged links between Donald Trump and Russia until the probe is complete, but did assert that he expects more Russian meddling in future US elections.

“I think one of the lessons the Russians may have drawn from this is that this works,” Mr Comey said. “I expect to see them back in 2018, and especially in 2020.”

When asked about what the FBI is doing to prepare for this, Mr Comey said that an enormous portion of the bureau's counter intelligence and cyber divisions focuses on “making sure that we do everything we can to understand how the bad guys might come at us”.

Ms Clinton said on Wednesday in New York that she takes responsibility for her election loss but believes the FBI email investigation played a key part.