WASHINGTON: Donald trump has sought to frame his presidential bid as a fight against "Washington insiders" as fresh waves of defectors from his own party issued dire warnings about the peril America would face with him in the White House.
Mr Trump lambasted 50 senior Republican national security officials who said he would be the "most reckless president ever", claiming they represented the "old guard" and the "failed Washington elite looking to hold onto their power".
Meanwhile, Susan Collins of Maine became the most senior Republican member of Congress to say she would not vote for the party nominee.
In a scathing critique she called the billionaire "unworthy" of office, and declared herself "increasingly dismayed by his constant stream of cruel comments, and his inability to admit error or apologise". The senator said she would not vote for Hillary Clinton, the Democratic nominee, but may consider supporting the Libertarian Party.
Former CIA spy Evan McMullin, a Republican running for president as an anti-Trump Independent, called him "inhuman, a fraud and a conman".
Mr McMullin's campaign said 50,000 people had signed up by email and money was "roaring in" from disaffected Republicans.
In response Mr Trump targeted the authors of the national security letter, including Michael Hayden, former director of the CIA and NSA.
He said: "The names on this letter are the ones the American people should look to for answers on why the world is a mess.
"They are nothing more than the failed Washington elite, Washington establishment people. It's time they are held accountable for their actions. They, along with Hillary Clinton, are the ones who allowed the rise of Isis."
Mr Trump said he won the primary contest for the Republican nomination by "fighting these insiders".
But Barry McCaffrey, a retired four-star general, declared Mr Trump unfit for office, saying it was "remarkable how little he knows" about national security. He added: "Why he's so out of the loop on these issues is hard to imagine."
Mr Trump fell further behind Mrs Clinton, with an NBC poll putting the gap at 10 oints, but the former First Lady faced her own campaign setbacks. Pat Smith and Charles Woods, the parents of two Americans who died in the 2012 attack in Benghazi, filed court papers suing Mrs Clinton for wrongful death. They claimed the loss of their loved ones was a direct result of her reckless handling of classified information when she was US secretary of state.
The Clinton campaign said there was "no evidence whatsoever of wrongdoing" and independent experts suggested the case would be dismissed.