Police near Parliament have been “briefed to intervene appropriately” if the law is broken after Tory MP Anna Soubry accused them of ignoring abuse hurled at politicians and journalists.

The pro-EU Tory made the allegation the day after she was branded a “Nazi” and a “liar” by a mob who targeted her during live television interviews and then followed her as she made her way back into the Commons.

It was the latest in a string of high-profile demonstrations targeting individual MPs in Westminster and prompted more than 50 MPs from across the Commons to write to Metropolitan Police Commissioner Cressida Dick on Monday night to express their “serious concerns” about the “deteriorating public order and security situation” outside Parliament.

BrexitPolice stand near pro-Brexit supporters outside Parliament (Kirsty O’Connor/PA)

On Tuesday, Metropolitan Police Deputy Assistant Commissioner Laurence Taylor said: “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 protesters, 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.”

The force is assessing whether any crime was committed by the protesters who hurled abuse at Ms Soubry and campaigners Owen Jones and Femi Oluwole on Monday.

Ms Soubry told Good Morning Britain on Tuesday that there was a small group of people “roaming around Westminster intimidating people going about their lawful business”.

The Broxtowe MP added that, while she anticipated a level of criticism and abuse as an MP, she expected authorities to act when it “crossed the line”.

She told GMB: “It crossed the line in December, it was journalists who were being attacked.

“(Sky News’ political editor) Faisal Islam, who is male, was racially abused by these people, it’s the same group, all on video, and the policy of the Metropolitan Police is to ignore it.”

The letter, signed by at least 55 MPs, criticised a “lack of co-ordination” in the response from the police and appropriate authorities despite assurances that incidents before Christmas would be dealt with.

The MPs 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.”

The attack on Ms Soubry was widely condemned on Monday, with Commons Speaker John Bercow saying he was “concerned” about a “pattern of protest” targeting female MPs and journalists.

Protesters could be heard chanting “Soubry is a Nazi” as she appeared on BBC News, prompting her to tell interviewer Simon McCoy: “I do object to being called a Nazi, actually.

“I just think this is astonishing, this is what has happened to our country. But let’s try and move on and be positive about things.”

BrexitPolice officers at Parliament Square in London as the Vote Leave bus passes by (Kirsty O’Connor/PA)

Protesters also chanted slogans including “Liar, liar” throughout a live interview with Ms Soubry on Sky News.

Earlier on Monday, political commentator Owen Jones shared a video on Twitter which showed him being accosted by a group outside Parliament, including men wearing Union flags.

They could be heard calling him a “traitor” and a “horrible little man” and accusing the Labour activist of writing “fake news”.

The incidents prompted a wave of criticism from politicians and commentators from across the political spectrum.