Suella Braverman has been referred to the financial service watchdog by Labour over claims she may have breached market abuse laws, as the home secretary also faced growing criticism for her “car crash” handling of a migrant processing facility in Kent. Fresh questions were raised about the “growth visas” announcement Braverman sent to several figures outside the government that led to her sacking nearly two weeks ago, with one Conservative MP openly saying they did not “accept or trust this home secretary’s word”. Labour claimed Braverman’s leak may have had significant economic repercussions, given the policy was designed to be factored into the Office for Budget Responsibility’s projections. In a letter seen by the Guardian, the shadow City minister, Tulip Siddiq, wrote to the Financial Conduct Authority (FCA) urging them to launch an investigation and argued the move could “tangibly influence financial markets”. She said there was a “case to answer”, as public interest and industry confidence in measures to prevent insider trading relied on trust they would be fully enforced. Simon Case, the cabinet secretary, was also urged to confirm whether he believed the law had been broken. Siddiq told him it was “not unreasonable to suggest” that the policy leak “could lead to insider trading on the value of sterling” and have other serious repercussions “if it fell into the wrong hands”. Given Downing Street had briefed journalists when Braverman was sacked on 19 October that the information she leaked was market-sensitive, Siddiq said breaching insider trading laws “does not require proof that market-sensitive information has been acted upon for gain”. Unlawful disclosure “is a serious offence in its own right”, she added. Braverman has denied the leaks were market-sensitive. Siddiq quoted FCA advice to government departments, which states that they “may hold information that is confidential, non-public and valuable”, which if handled incorrectly could lead to “disorderly markets” and “market abuse, such as insider dealing”. While the guidance says that the law is not being broken if information is disclosed “in the normal exercise” of employment, Siddiq said it was “difficult to see that the disclosure of market sensitive, confidential, significant policy from a personal email address to someone outside of government is included in this exception to the rules”. Six days after her re-appointment as home secretary by Rishi Sunak, Braverman confirmed that she had forwarded a draft written ministerial statement about the launch of growth visas by Liz Truss’s government to a backbench MP, Sir John Hayes, and another colleague’s parliamentary staffer. Given the admission, Siddiq said the FCA should launch an investigation into whether Braverman broke market abuse laws or regulations, and confirm that senior ministers should show the highest standards of protecting market-sensitive information. A source close to the home secretary said she had been clear that “the information was not market sensitive as all the data was already in the public domain”. They added: “The Labour party would seemingly rather snipe from the sidelines about issues that are not the priorities of the British people they claim to represent rather than focus on how to bring down illegal migration into the UK, for which they have no plan.” The Tory MP Roger Gale claimed Braverman was “only really interested in playing to the right wing” and told Times Radio he was dubious about her denial she dismissed legal advice about overcrowding at the facility in Manston. “I do not accept or trust this home secretary’s word,” Gale said. Meanwhile, Braverman faced further criticism from Home Office staff for her language in the Commons on Monday. After a petrol bomb was thrown at a migrant facility in Dover, officials privately raised concerned that her remarks could encourage further attacks on official buildings – endangering employees and people seeking refuge in the UK. A staff member who works near to the site that was firebombed said Braverman’s description of the increase as an “invasion” had made staff on the south coast feel nervous. “This guy drove down from High Wycombe to commit this act,” they said. “He is one of a lot of people who are becoming angry about immigration, and the numbers coming to the UK. And then they hear the home secretary saying there is an invasion along this coast. “It seems so irresponsible for a person in her position to reinforce what they are reading on social media. Inevitably, some will start thinking that we are part of the problem because we are supposed to be dealing with the situation. We work in buildings with little security, and feel very exposed.” Another senior Home Office source from the department’s London headquarters said: “People here are furious.” They added: “We can’t believe that she is using the inflammatory language that many of us were told we couldn’t use, full stop. If we used language like ‘swarmed’ to a colleague we could face disciplinary procedures. But she is allowed to use it in parliament?” Sources on the ground at Manston said that by around midday on Tuesday the numbers of asylum seekers being held on site had fallen to about 3,600, while the number of marquees in use had risen from 22 to 30. Cleaning had started to take place in parts of the site, the sources added. Rishi Sunak’s spokesperson did not criticise Braverman for her comments, and claimed she was seeking to express the “sheer scale of the challenge”. The spokesperson also claimed a “significant proportion” of people arriving were economic migrants – but could not provide any evidence or data.