'This is just unheard of and unprecedented': Former CIA director slams Trump's rift with the intel community
"I've been in public service for over 50 years. I have never seen anything like this in my lifetime," said Panetta, who served as CIA director from 2009 to 2011 and as Defense Secretary from 2011 to 2013.
"The fact that the President-elect is tweeting about these issues, and taking it to the public - and in many ways undermining the credibility of the very intelligence agencies that have to provide information to him in order for him to be President of the United States - this is just unheard of and unprecedented," Panetta said.
"Very frankly, if a president is going to be successful, this is no way to start," he added. "The president's got to make tough decisions. He cannot make those tough decisions without the very best intelligence that can be provided to him."
Trump has downplayed the US intelligence community's conclusion that Russia orchestrated the hacks on the Democratic National Committee and Hillary Clinton's campaign chairman, John Podesta, during the presidential campaign.
He has promoted the idea that the hacks could have been carried out by a "14-year-old" or "a guy sitting on their bed who weighs 400 pounds." He has also floated the idea that the CIA's conclusions could be wrong, based on past faulty intelligence assessments involving the Iraq war.
"These are the same people who said Saddam Hussein has weapons of mass destruction," Trump said in a statement last month.
Last weekend, Trump made this point again to reporters gathered at his Mar-a-Lago estate in Florida.
"If you look at the weapons of mass destruction, that was a disaster and they were wrong," he said.
Two days later, Trump tweeted that it was "very strange" that "the 'Intelligence' briefing on so-called 'Russian hacking' was delayed until Friday."
"Perhaps more time needed to build a case," Trump said, though intelligence officials denied the briefing had been delayed.
On Wednesday, Trump again cast doubt on the US intelligence community's conclusion that Russia orchestrated the hacks. He cited a Fox News interview with WikiLeaks founder Julian Assange, who said Russia did not feed the stolen documents to the self-described transparency organization.
"Julian Assange said 'a 14 year old could have hacked Podesta' - why was DNC so careless?" Trump tweeted. "Also said Russians did not give him the info!"
Three intelligence officials on Thursday told Reuters, citing a final CIA report on the election-related hacks, that the agencies had identified Russian officials who gave the documents to WikiLeaks at Russian president Vladimir Putin's instruction.
Panetta told "Today" that the president-elect cannot "seriously" address the country's national security concerns via Twitter, and that "this is not the kind of bickering that ought to be going on in public."
"When he sits down with the intelligence community and hears what they have to say, I think he's going to realize that this is a very important issue that must be dealt with seriously," Panetta said.
"He's going to find that it's easy to tweet about reactions to all kinds of issues, but to seriously deal with our national security and deal with the threats of our country is a business that's ought to be done in the confines of the Oval Office."