Jim Acosta, the CNN chief White House correspondent whose public confrontations with Donald Trump went viral, has warned that it is a dangerous time to tell the truth in the US.

Acosta defended his heated interactions with Trump and slammed the president and his administration for continuing to describe the press as the enemy of the people and for claiming CNN were purveyors of “fake news”.

Speaking at an event at the Oxford Union in the UK, Acosta said: “Perhaps they won’t stop calling us the enemy of the people because it works so well with their people, but all of this adds up to one painful reality: this is a dangerous time to tell the truth in America.”

He added that those who continued to use that rhetoric create “an atmosphere where people can get hurt, where journalists can get murdered.”

Acosta has had a number of public clashes with Trump in the last two years of his presidency. Last year, his White House pass was suspended after the president tried to shut down further questions from the correspondent and Acosta insisted on asking follow-ups. The argument led to a tugging match between a White House intern who tried to take the microphone from Acosta, who hung on to it.

After Acosta sat down, Trump said: “I tell you what, CNN should be ashamed of itself, having you working for them.” He went on: “When you report fake news, which CNN does a lot, you are the enemy of the people.”

It wasn’t the first time Trump accused Acosta of fake news. During his pre-inauguration press conference, Trump had refused to take a question from Acosta, saying: “Not you. Your organisation is terrible.” Though Acosta repeatedly asked to be allowed a question, Trump refused. “I’m not going to give you a question. You are fake news,” he said.

The row escalated after the White House then suspended Acosta’s pass, accusing the correspondent of assaulting the intern.

In response to the incident, Acosta said: “The vast majority of people could plainly see the only thing that was under assault that day was the truth.”

The White House was eventually forced to back down and give Acosta his pass.

Acosta went on to describe Fox News as “beast of many heads”. While Acosta said journalists on Fox News had defended him when he had his press card revoked, he added that there are “forces on that network that act as propagandist for Trump”. He said journalists from Fox News have privately sent him supportive messages, but wished they would do so publicly.

Acosta also spoke of his shock when Trump praised Greg Gianforte, the Congress member from Montana, for violently attacking Guardian reporter Ben Jacobs, telling supporters at the rally that someone who performs a body slam is “my guy”. Trump’s comments mark the first time the president has openly and directly praised a violent act against a journalist on American soil.

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Acosta, who was in the press pen during the rally, said: “One of them started making body slam gestures and then he ran his thumb across my neck like he wanted to slit my throat. This is not the first time I felt threatened at his rallies.”

When asked if he was being too aggressive when he engaged with Trump and his administration, Acosta said there is a reasonable expectation that reporters are going to be tough and aggressive.

“Are we supposed to roll over? Are we supposed to take it?” Acosta asked. “Some colleagues say to just take it, but I’m still thinking about the folks at home, thinking about my own kids, are we supposed to let the bully beat us up at the playground every day?”