Labour MP Stephen Doughty penned a letter to Met Police boss Cressida Dick.
It has been signed by a cross-party group of at least 55 MPs — including Brexiteers and Remainers.
This comes after Tory MP Anna Soubry was called "Nazi" by protesters during live TV interviews with BBC and Sky News yesterday.
Cops are now investigating if any crime were committed during the clash outside Parliament on College Green.
“We write to express our serious concerns about the deteriorating public order and security situation”
The MPs' letter
Ms Soubry has accused the Metropolitan Police of ignoring abuse — including racism — hurled at politicians and journalists.
Speaking to Good Morning Britain today she slammed protesters "roaming around Westminster intimidating people going about their lawful business".
The pro-EU Broxtowe MP added that while she expected a level of criticism and abuse as an MP, authorities must act when it "crosses the line".
She told GMB: "It crossed the line in December, it was journalists who were being attacked.”
Speaking about racist abuse Sky News journalist Faisal Islam received, Ms Soubry said police policy “is to ignore it”.
MPs said security fears had been "repeatedly raised" with officers and senior policing staff.
The letter said: "We write to express our serious concerns about the deteriorating public order and security situation in and around the exterior of the Parliamentary estate including College Green.
"After months of peaceful and calm protests by groups representing a range of political views on Brexit, an ugly element of individuals with strong far right and extreme right connections – which your officers are well aware of – have increasingly engaged in intimidatory and potentially criminal acts targeting Members of Parliament, journalists, activists and members of the public.
"We understand there are ongoing investigations but there appears to be an ongoing lack of coordination in the response from the police and appropriate authorities including with Westminster borough policing – and despite clear assurances this would be dealt with following incidents before Christmas – there have been a number of further serious and well publicised incidents today."
Speaker John Bercow said the far-right mob were "members of assorted groups that have donned the yellow vests seen in France" – linking the abuse to "gilet jaune" anti-government riots.
Deputy Assistant Commissioner Laurence Taylor for Met Operations said: “Police continue to assess if any crimes have been committed following a third party report of a public order offence on Monday, 7 January, in the area of College Green, SW1.
“If a crime has been committed the matter will be fully investigated. There has been no arrest at this stage.
“An ongoing policing operation at the Parliamentary estate around Brexit continues and we have an appropriate policing plan in place.
“Our role is to facilitate peaceful protest and balance the needs and rights of all those present, including protestors, MPs and members of the public.
“We will deal robustly with incidents of harassment and abuse against anyone where that harassment or abuse constitutes a criminal offence.
“Officers in the area have been briefed to intervene appropriately where they hear or see breaches of the law.“