The Commons Speaker has demanded police tackle the "aggressive, threatening and intimidating behaviour" towards politicians and journalists outside Parliament.
John Bercow hit out at "toxic attacks" in a letter to Metropolitan Police Commissioner Cressida Dick the day after MP Anna Soubry was branded a Nazi by a mob during television interviews.
He said he supported more than 50 MPs who also wrote to Ms Dick to express their "serious concerns" about the "deteriorating public order and security situation" outside Parliament".
In his letter to Ms Dick, the Speaker John Bercow said: "It is, frankly, intolerable if Members of Parliament and journalists cannot go about their lawful business without being ritually insulted, abused, intimidated, threatened and harassed.
"There seems to be a pattern here of a regular coterie of burly white men who are effectively targeting and denouncing Members whom they recognise and dislike - most notably female and those from ethnic minority backgrounds."
Speaking in the Commons as the letter was published, Mr Bercow described the intimidation as "a type of fascism".
It comes as tensions in Westminster continue to heighten before a vote on the Prime Minister's Brexit deal next week.
In a statement on Tuesday, the Metropolitan Police said it would "continue to assess" whether a crime had been committed.
"An ongoing policing operation at the Parliamentary estate around Brexit continues and we have an appropriate policing plan in place," Deputy Assistant Commissioner Laurence Taylor said.
"Our role is to facilitate peaceful protest and balance the needs and rights of all those present, including protesters, MPs and members of the public."
Meanwhile, amendments will be submitted to the Budget-enacting Finance Bill which returns to the Commons on Tuesday in an attempt to block a no-deal Brexit.
The amendment tabled by Labour former cabinet minister Yvette Cooper and Conservative ex-education secretary Nicky Morgan would restrict the Government’s freedom to make Brexit-related tax changes without parliamentary safeguards.
It came as:
Sources close to Jeremy Corbyn suggested Labour would join senior MPs in backing a parliamentary campaign to rewrite Government legislation to block a no-deal Brexit.
Liberal Democrat leader Sir Vince Cable warned of “untold disruption” if Britain crashes out of the EU without a deal.
The Government will begin broadcasting radio adverts to help people prepare for Brexit, focusing on topics including passports, visas, healthcare and driving in the EU.
Mrs May, who will chair a meeting of Cabinet on Tuesday morning, said she was seeking “further assurances” from Brussels to help get her deal through the Commons.
Former Ukip leader Nigel Farage, who has regularly faced abuse from protesters, told ITV's Good Morning Britain that public figures "should be free to go out and express their opinion without the threat of violence".