Boris Johnson’s senior adviser Dominic Cummings has said it is "not surprising" people are angry at MPs.
Mr Cummings, like Mr Johnson, refused to back down in the ongoing row over the tone of political debate in Westminster.
Mr Johnson has come under intense pressure for his remarks in the Commons chamber, including saying the best way to honour murdered MP Jo Cox is to “get Brexit done”.
Mr Cummings, speaking on Thursday evening at the central London launch of a new book by Vote Leave supporter Stuart Wheeler, was asked if he blamed MPs for the abuse they are receiving.
He 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. How does that compute for them?”
He went on: “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?"
When asked directly if the MPs have themselves to blame for the abuse, Mr Cummings said: "That's the way you're putting it. I am using my language."
He added that “in the end the situation [of threats against MPs] can only be resolved by Parliament honouring its promise to respect the result."
On Thursday, Labour MP Jess Phillips said a man was arrested after trying to "kick the door" of her constituency office while reportedly shouting that she was a "fascist".
Liberal Democrat leader Jo Swinson, meanwhile, was speaking to police following threats made to one of her young children.
And in a viral Twitter thread, Ellie Cooper, the daughter of senior Labour MP Yvette Cooper, described her fears for her mother in the wake of Ms Cox's murder. She accused Mr Johnson of "using language that helps incite violence toward MPs".
