The Democrat nominee for president, Hillary Clinton, made a mistake using her personal email for official Secretary of State business, but said it was not “a cause for distrust”, according to her husband and former White House occupant Bill Clinton.

During a question-and-answer session in Las Vegas while campaigning for his wife, the former president said Ms Clinton's use of her own private email server for government communications, rather than an official one, was something her predecessors and successors had done.

However, he added that she should have known she would be subjected to higher levels of scrutiny if she planned to run for president.

He said it would not have occured to diplomats at the time that they should be concerned with records classification and insisted the issue, which has cast a shadow over Ms Clinton’s campaign, was not “a cause for distrust”.

“If it were a cause for distrust, it's inconceivable that all these prominent national security people...would've endorsed her,” he added.

Ms Clinton has argued the email system was set up for convenience, but critics have said it allowed her to control which messages she sent and received as Secretary of State were recorded by the State Department.

Over 30,000 emails were subsequently handed over to the State Ddepartment, while 30,000 more were deemed private and personal and were deleted, Sky News reported.

Opponents have suggested some of the deleted emails may relate to the 2012 attack on the US consulate in Benghazi, Libya, in which the US ambassador Chris Stevens and three other Americans were killed.

The FBI subsequently said Ms Clinton was “extremely careless” in the way she handled “very sensitive, highly classified information”.

Amid the row, Ms Clinton has published her tax return and challenged her Republican opponent Donald Trump to do the same.

But Mr Trump’s communications adviser Jason Miller said people were more interested in seeing Ms Clinton’s deleted emails.

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