USA Today has branded Donald Trump 'unfit for the presidency' as the media organisation's editorial board took sides in the presidential election race for the first time in its 34 year history.

The board said it had never previously seen any reason to alter its no-endorsement policy for the elections.

However, it said it had changed its mind after Mr Trump 'demonstrated repeatedly' that he was not fit to be president.

Read more: In full - USA Today's editorial on why Donald Trump is 'unfit for the presidency'

In an editorial on the USA Today site, the board said: "From the day he declared his candidacy 15 months ago through this week’s first presidential debate, Trump has demonstrated repeatedly that he lacks the temperament, knowledge, steadiness and honesty that America needs from its presidents.

"Whether through indifference or ignorance, Trump has betrayed fundamental commitments made by all presidents since the end of World War II. These commitments include unwavering support for NATO allies, steadfast opposition to Russian aggression, and the absolute certainty that the United States will make good on its debts.

"He has expressed troubling admiration for authoritarian leaders and scant regard for constitutional protections."

Read more: How Donald Trump (or Hillary Clinton) could win despite having fewer votes

The board also included a list of eight reasons why Mr Trump should not be President in its editorial. These included claims that he was erratic, a serial liar, and ill-equipped to be commander in chief.

However, the US media outlet made it clear that its decision to hit out at Mr Trump did not mean it was supporting Hillary Clinton.

Read more: In full - USA Today's editorial on why Donald Trump is 'unfit for the presidency'

The board said that Ms Clinton 'has her own flaws' and it did not 'have a consensus for an endorsement', adding it had serious reservations about the Democratic candidate's 'sense of entitlement, her lack of candor and her extreme carelessness in handling classified information'.

Mr Trump and Ms Clinton met for their first television debate earlier this week, with the Republican candidate going on the defensive after saying he would 'try and wing' it.

The latest polls show Ms Clinton received a boost from her debate performance, giving her a three point lead over Mr Trump nationally.