President Obama used a code name to communicate with Hillary Clinton on her controversial email server in 2012 - appearing to contradict claims he 'found out at the same time as everybody else'.

According to FBI investigators, Clinton's top aide Huma Abedin understood the significance of this immediately when told during questioning and exclaimed, 'How is that not classified?'.

Indeed, documents released by the FBI on Friday reveal that when Abedin learned her boss had allegedly exchanged messages with the president on an un-secure channel, using a pseudonym to protect his identity, she demanded her own copies.

This was presumably to cover her own back in case top secret information had been discussed, which would potentially be criminal.

'This exchange strongly suggests Clinton and the president knowingly discussed classified material in an unclassified setting and hence broke the law,' Raj Shah, the research director at the Republican National Committee, told the New York Post.

The White House knew Hillary Clinton used a private email account and President Obama used a pseudonym to communicate with her, new FBI documents reveal

Clinton aide Huma Abedin revealed to the FBI that the White House had to be informed when the Democratic presidential nominee changed her primary email address.

The White House server could only receive emails from designated accounts and one of them had to be Clinton's, who was Secretary of State at the time.

Obama claimed in March 2014 that he only found out Clinton was using a private account for official State Department business through a New York Times report.

The president told CBS News that he found out about the emails 'the same time everybody else learned it through news reports'.

Abedin revealed to the FBI that she did not know what Obama's pseudonym was and did not recognize his email address when she was shown an exchange between Clinton and the president in 2012.

The June 2012 exchange, which took place on Clinton's private account, had the subject 'Re: Congratulations!', according to the Daily Beast.

When Abedin was informed by the FBI that it was believed the pseudonym belonged to Obama she exclaimed, 'How is this not classified?', the FBI report states.

'Abedin then expressed her amazement at the president's use of a pseudonym and asked if she could have a copy of the email', the report continues.

The FBI released 189 new pages from its investigation into Clinton's private email server on Friday night.

Emails between Clinton and Obama are exempt from the disclosure, citing 'presidential communications privilege'.

The FBI report does not detail the particular email that was shown to Abedin.

But, due to the date of the email, it may be related to a Supreme Court ruling that day which upheld a portion of the Obamacare law, according to Politico.

The exchange had the subject 'Re: Congratulations!' and took place in June 2012, on the day the Supreme Court upheld a portion of the Obamacare law

Human Abedin revealed to the FBI that the White House was informed when Clinton changed her primary email address as it could only receive messages from designated accounts

The Republican National Committee immediately jumped on the report, saying it was evidence Clinton and Obama both broke the law.

'This exchange strongly suggests Clinton and the president knowingly discussed classified material in an unclassified setting,' RNC research director Raj Shah told the New York Post.

But Clinton spokesman Brian Fallon said the email illustrated how insignificant the items in the presidential hopeful's private email server really were.

'These materials further demonstrate why the Justice Department believed there was no basis to move forward with this case,' Brian Fallon said.

The report also contains an interview with a Romanian hacker known by the name of 'Guccifier', who revealed he had lied to Fox News about hacking into Clinton's server.

'Lazar began by stating that he had never claimed to hack the Clinton server,' the report reads.

'[An FBI agent] then advised that Fox News had recently published an article which reported that Lazar had claimed to have to Clinton server.'

'Lazar then stated that he recalled the interview with Fox News, and that he had lied to them about hacking the Clinton server.'