It is “not surprising” there is anger directed at MPs over Brexit, the PM’s adviser Dominic Cummings has said.
The former Vote Leave chief said the only way the issue of abuse will be solved is if MPs “respect” the result of the EU referendum.
Mr Cummings’s remarks came after Boris Johnson defended his use of language in Parliament amid criticism from MPs.
On Wednesday, Mr Johnson dismissed a Labour MP’s complaint that his language risked provoking attacks as “humbug”.
MPs criticised a number of comments Mr Johnson made during an ill-tempered debate in the House of Commons, the day after the Supreme Court ruled the prorogation of Parliament was unlawful.
Meanwhile, the daughter of Labour MP Yvette Cooper has made an emotional plea to politicians over their language, saying she is “scared every single day” for her mother’s safety.
And a man has been arrested for allegedly verbally abusing staff at Labour MP Jess Phillips’ constituency office in Birmingham.
At a book launch on Thursday evening, Mr Cummings said: “The MPs said we will have a referendum, we will respect the result and then they spent three years swerving all over the shop.
“It is not surprising some people are angry about it. I find it very odd that these characters are complaining that people are unhappy about their behaviour now and they also say they want a referendum.”
He added: “If you are a bunch of politicians and say that we swear we are going to respect the result of a democratic vote, and then after you lose you say, ‘we don’t want to respect that vote’, what do you expect to happen?”
He said both Leave and Remain campaigners had received “serious threats” of violence, which he said should be taken seriously.
“In the end the situation can only be resolved by Parliament honouring its promise to respect the result,” he said, echoing the prime minister’s words in the Commons.
“Believe me,” Mr Johnson told MPs. “The best way to ensure that every parliamentarian is properly safe and to dial down the current anxiety in this country is to get Brexit done.”
PM ‘deplores threats’
Mr Cummings also said Downing Street was “not under pressure”.
“This is a walk in the park compared to the referendum, we are enjoying this, we are going to leave and we are going to win,” he said.
Earlier, a video showed Labour shadow minister Karl Turner approaching Mr Cummings and urging him to dial down the “inflammatory” language used by the prime minister.
Labour leader Jeremy Corbyn warned that the PM’s language was encouraging people to behave in a “disgraceful and abusive way”, as MPs debated the use of language in the Commons on Thursday.
In the debate, several MPs said the prime minister should apologise for saying the best way to honour MP Jo Cox, who was murdered during the EU referendum campaign, was to “get Brexit done”.
MPs also detailed some of the threats they had faced, with Tory MP Caroline Noakes describing how someone called her a “traitor who deserved to be shot” on a walkabout in her constituency.
But Mr Johnson insisted he “deplores any threats to anybody, particularly female MPs”, and he said that “tempers need to come down” in Parliament.