Britain’s top lawyers have written to Priti Patel to express their concern after a knifeman threatened to kill an immigration solicitor last month in an attack colleagues say was directly motivated by comments made by the home secretary. On 7 September a man with a large knife entered a London law firm and launched a “violent, racist attack” that injured a staff member before the assailant was overwhelmed. A confederate flag and far-right literature were allegedly found in a bag he was carrying. According to documents about the incident, police described the knife as a “weapon designed to cause serious harm”. Days before, on 3 September, Patel dismayed the legal profession by claiming “activist lawyers” were frustrating the removal of migrants. It was Patel’s remarks which the law firm – not being named for security reasons – believe inspired the incident. “Responsibility and accountability for this attack, in the eyes of this firm, lies squarely at the feet of Priti Patel,” say documents containing witness statements and details of the attack. The day after the incident, the firm wrote to the Law Society asking it to raise the issue with Patel, government lawyers, the lord chancellor and the Ministry of Justice to “ensure that public attacks on the legal profession are prevented from this point forth”. The letter said: “It must be ensured that no further lives are endangered as a result of her untruthful and deliberately inflammatory rhetoric. Put simply, this must stop now, before innocent lives are taken and other irreparable damage is done to those who work in this field.” It added: “This must involve all previous statements made by Priti Patel being publicly retracted, and an apology or acknowledgment that such action to date has been inappropriate. Urgent reassurance is required from the government that this will not be repeated. The position as it stands is untenable, dangerous, and cannot be allowed to persist.” On Saturday the Law Society confirmed it sent correspondence last month on the attack to the Home Office and Ministry of Justice. Patel appears not only to have ignored its concerns but doubled down on her attacks against immigration lawyers. Last Sunday, almost a month after the knife attack, Patel used her speech at the Conservative party conference to target “do-gooders” and “lefty lawyers,” claiming those who represented asylum seekers were “defending the indefensible”. Two days later, in his keynote speech, Boris Johnson went even further, claiming the entire criminal justice system was “being hamstrung by lefty human rights lawyers”. It remains unclear to what extent, if any, the PM was aware of the knife attack. Last night the body representing the legal profession reminded the government that inflammatory rhetoric had consequences. The Law Society revealed it had heard from other law firms which had received increased “levels of abuse, threats and hostility” in response to the intervention of the home secretary and PM. It also emerged that some immigration law firms have been forced to hire security guards and introduce protective measures for staff. One, whose anonymity was granted for safety reasons, said: “We’re not being cowed but we’re taking precautions and have upped security because we have received threats. “We’ve had to be more vigilant and brought in security in our offices and we’ve had to report certain social media posts and inform the police who have been very supportive.” The documents on last month’s attack reveal that a receptionist at the firm was “assaulted and wounded” and “a number of our staff members are fortunate to be alive [and] not to have suffered serious injury.” The documents add: “The attack was intended to take the life of a member of the Law Society.” A 28-year-old man has been charged with possession of, and making threats with, a bladed article in a public place; racially aggravated public disorder; assault; and making threats to kill in connection with the incident. Yesterday the Law Society of England and Wales warned that it was already witnessing the consequences of comments made by the prime minister and home secretary. President Simon Davis said: “We are extremely concerned about the safety of solicitors and barristers in the current climate, firms that deal in emotive issues such as immigration are being targeted. “We are monitoring the situation closely and urge both government and media to be mindful of the rhetoric they employ. The role of solicitors is to apply and uphold the laws set down by parliament and they have a right to do so on behalf of their clients without intimidation.” Pressure on Johnson intensified on Saturday when the chair of the Bar Council, Amanda Pinto QC, wrote to the prime minister urging him to withdraw his comments. She said: “I deplore your remarks at the Conservative party conference which wrongly seek to politicise and attack lawyers for simply doing their job in the public interest.” The letter, seen by the Observer and also sent to Patel, attorney general Suella Braverman and justice secretary Robert Buckland adds: “I urge you to withdraw your comments and to reassure thousands of key workers – including lawyers employed by your own government – that they are not being attacked by their prime minister for their important contribution to the justice system.” On Friday even the Home Office official Twitter account continued to take aim at immigration lawyers, conflating foreign nationals with asylum seekers and complaining that attempts to deport the latter were “frustrated by legal claims”.