The number of crimes soared to 152 between January and April this year, a parliamentary inquiry was told – a rise of 90 per cent compared with the same period last year.
Cressida Dick, the Metropolitan Police commissioner, described the scale and ferocity of the attacks – including on prominent pro-EU women MPs Jess Phillips, Anna Soubry and Sarah Wollaston – as “extraordinary”.
Alongside her, the head of UK counterterrorism policing, Neil Basu, acknowledged that the anger provoked by Brexit was a “huge driver” behind the increase.
He said there was a “very clear pattern” of misogyny and racism driving the abuse, revealing just 10 MPs accounted for 29 per cent of all the reports.
MPs had been asked to report all incidents, to enable the police to identify “hotspots”, with more than 600 logged so far this year.
A notorious level of abuse was also hurled at Ms Soubry, another Tory switcher to Change UK, as she walked near parliament earlier this year.
This week, police launched an investigation into a Ukip European election candidate who repeatedly made comments about raping Ms Phillips, a Labour MP.
West Midlands Police said it had received a report of malicious communications after Carl Benjamin, a YouTuber who uses the name Sargon of Akkad online, discussed sexually assaulting the politician in a video.
Mr Benjamin had previously refused to apologise for tweeting Ms Philips in 2016 after she had discussed rape and death threats sent to women over the internet, telling her he “wouldn’t even rape” her.
He has repeatedly refused to row back from the comments since his selection as a Ukip MEP candidate in the South West region, insisting he would refuse to “apologise for my crimes against political correctness.”
However, in a video posted on YouTube late last month, he said he had been “in a lot of trouble for my hardline stance of not even raping [Ms Philips].”
“I suppose with enough pressure I might cave. But let’s be honest nobody’s got that much beer,” he added.
Ms Phillips later told the BBC she had broken down in tears in public after learning of the YouTuber’s latest comments.
“It sort of dawned on me that, for four years essentially, this man had made a career out of harassing me,” she said.
“And I felt harassed. I felt, ‘How can somebody say that they would rape me if forced, and be a legitimate candidate in an election?’”
Ms Dick told the human rights committee that the murder of Labour MP Jo Cox in 2016 had contributed to an “extraordinary set of circumstances” with a level of harassment and abuse not seen before.
“Polarised opinion” on political and social issues was also having “a big impact on the scale and impact of protest activity”, she added.
However, Ms Dick, while admitting officers were “too passive” when dealing with protesters who barracked Ms Soubry, insisted the situation had now changed.
The police were determined to ensure MPs were able to go about their business and that the rights of protesters are not “unfettered”.
“We do believe that our posture generally at the time that you are talking about, just before Christmas and just after, was overall too passive,” the Met chief said.
“Since then you will have seen a very big step up in the resourcing of the policing of the protests around parliament.”
On an average day, there are now around 60 officers dedicated to policing protests around the Houses of Parliament, and they were “more interventionist”.
Ministers have said they intend to pass a law creating a specific new criminal offence of intimidating parliamentary candidates and party campaigners.
Under the proposals, anyone found guilty of harassing or abusing candidates or their officials during UK-wide elections would be liable to appropriate criminal penalties.
Mr Basu said Brexit was a driving force behind many of the reports this year, but said 43 per cent of crimes had been targeted against those in favour of leaving the EU, with 47 per cent aimed at Remainers
Giving evidence to the same committee, Max Hill QC, the director of public prosecutions at the Crown Prosecution Service, revealed spending on security for MPs increased more than 100-fold over the last decade.
Security assistance rose from just £37,000 in 2010-11 to £4.2m in 2017-18, reflecting the “changing nature” of the threats to MPs, he said.