The Archbishop of Canterbury has warned Boris Johnson and other MPs to avoid using inflammatory language - as the UK prepares for a general election.
Justin Welby said it was "extraordinarily dangerous for politicians to use careless comments" in a "polarised and volatile" society.
He told the Sunday Times that use of words like "traitor" and "fascist" had left MPs fearing for their lives.
The PM had a special responsibility to moderate his language, he added.
Last month, the prime minister was criticised for using words such as "surrender" when discussing Brexit.
Mr Johnson was also accused of dismissing abuse fears of female MPs as "humbug".
The PM later told the BBC that there had been a "misunderstanding" over his intention in using the word - which he apologised for.
Asked about Mr Johnson's use of the word "humbug", Archbishop Welby said he was "shocked" and that such concerns "should never be dismissed in that way".
"Death threats are really serious and they need to be taken seriously," he said.
"All sides need to say, 'That is totally and utterly unacceptable'."
Archbishop Welby added that "inflammatory words" had been said by politicians and voters on all sides of the political divide - which then risked being "amplified" by social media.
"I think we have become addicted to an abusive and binary approach to political decisions: 'It's either this or you're my total enemy'."
The Archbishop said that many MPs and peers had approached him for guidance after being driven to "the end of their tether" by the Brexit process, which has seen some expelled from their party.
"The stress is enormous. And they're being threatened a great deal and they're finding age-old friendships breaking down."
The Jo Cox Foundation - set up in memory of the MP who was murdered in 2016 - has called for an MP code of conduct, including use of language, to help protect politicians.
And Archbishop Welby has called for action to heal divisions "at almost every level of society", saying: "I don't only blame government."
His comments follow the release of latest Home Office figures which showed there has been a 10% rise in hate crimes recorded by police in England and Wales over the last year.