One of the reporters who helped expose Richard Nixon's involvement in the Watergate scandal has claimed that Donald Trump's attacks on the press "are more treacherous" than those of his predecessor.

Carl Bernstein, whose expose of clandestine and often illegal activities undertaken by members of the Nixon administration with Bob Woodward led to the US leader's 1974 resignation, said that Mr Trump's choice of language brought to mind “dictators and authoritarians, including Stalin, including Hitler”.

“Trump's attacks on the American press as 'enemies of the American people' are more treacherous than Richard Nixon's attacks on the press,“ former Washington Post reporter told CNN.

While Mr Nixon tended to attack his enemies in private, Mr Trump regularly broadcasts his views on the press to his 25 million Twitter followers, Mr Bernstein said.

He added that Mr Trump's rhetoric is potentially more dangerous than Mr Nixon's attacks on the news media because it is more public.

“There is no civic consensus in this country like there was at the time of Watergate about acceptable presidential conduct," he said. “Trump is out there on his own, leading a demagogic attack on the institutions of free democracy,“ he said. “We are into terrible authoritarian tendencies.”

Mr Bernstein spoke out against Mr Trump's behaviour after the president escalated his ongoing war on the mainstream media with a single tweet.

Mr Trump's dealings with the media have always been fraught, but his incendiary tweet followed a particularly chaotic press conference in which he called the assembled journalists "dishonest" and accused a Jewish reporter of lying before ordering him to sit down.

He also asked a black reporter asking about the Congressional Black Caucus: “Are they friends of yours? Set up a meeting.”

His use of "enemy of the American people" drew comparisons with despots like Stalin and Mao Zedong, who had a habit of using the phrase about opponents shortly before they died or “disappeared”.

It's “how dictators get started,“ Senator John McCain said the same day on NBC's show Meet the Press, of Mr Trump's comments.

Before the election, the University of Maryland's chair of broadcast journalism discerned “Nixon's echo—and, perhaps, Nixon's revenge“ in Mr Trump's rhetoric on the campaign trail.

“He, too, obsessively sought to manipulate the news coverage he desperately craved and wasn’t afraid to use intimidation if he thought it would help,” Mark Feldstein wrote in The Washington Post.

Mr Nixon's attacks on the press struck a chord with voters, helping carry him to power and encouraging more of the same, Mr Feldstein wrote.

“Nixon’s conduct in office presents a chilling example of what a President Trump could do,“ he said.

In 1971, Mr Nixon told the chairman of the Joint Chiefs of Staff, "the press is your enemy", according to a 1971 Oval Office tape quoted in the Washington Post. “Enemies. Understand that? … Now, never act that way … give them a drink, you know, treat them nice, you just love it, you're trying to be helpful. But don't help the bastards. Ever. Because they're trying to stick the knife right in our groin.”

But unlike Mr Nixon, Mr Bernstein emphasised that Mr Trump was not speaking to one person—the tape was only made public later—but to his 25 million Twitter followers when, after weeks of news reports on scandals and chaos in his White House, he called most of the major news organisations in the United States "enemies of the American People!"

“We're not enemies of the American people,” Mr Bernstein said on CNN. “In fact, we're the last resort of the American people to a dictatorial and authoritarian-inclined president.“