Suella Braverman has described the demonstrators taking to the streets in support of a ceasefire in Gaza as being involved in “hate marches”. In words that will anger some peace campaigners, the home secretary said “tens of thousands of people” had taken to the streets and had “chanted for the erasure of Israel from the map”. Speaking after a Cobra meeting chaired by Rishi Sunak on Monday, Braverman said: “We’ve seen now tens of thousands of people take to the streets after the massacre of Jewish people, the single largest loss of Jewish life since the Holocaust, chanting for the erasure of Israel from the map. “To my mind there is only one way to describe those marches: they are hate marches.” Her words appear to be a reference to the chant “From the river to the sea, Palestine will be free”. The slogan has been used for decades by pro-Palestinian campaigners and refers to the territory between the River Jordan and the Mediterranean Sea in historic Palestine. Some supporters of Israel have said it in effect calls for the destruction of Israel and the murder of Israelis. Braverman repeated a previous demand that police officers should take a “zero-tolerance approach to antisemitism”. However, police and human rights lawyers have said that the courts will struggle to convict anyone chanting the slogan without a change in the law. Scotland Yard told the Observer last week it was unlikely to arrest those who chanted the slogan at the march, knowing this would mean detaining thousands, some of whom see it as innocently calling for Palestinian self-determination. Braverman’s comments were described as irresponsible and careless by the shadow home secretary, Yvette Cooper. “The home secretary has a responsibility to make it easier for the police to tackle hate crime and extremism while reassuring different communities who are deeply distressed by events in the Middle East not to use rhetoric carelessly in a way that makes the job of the police much harder,” she said. “Antisemitic and Islamophobic hate crime and the glorification of terrorism need to face the full force of the law. At the same time work is needed to rebuild community cohesion, to recognise the distress people are feeling about the Hamas attacks and the humanitarian emergency in Gaza, and to pull communities together at this difficult time.” On Monday, the prime minister and the home secretary met with national security officials and police in Whitehall. Counter-terror officials are focused on whether Iran is trying to take advantage of heightened tensions in the UK caused by the Israel-Hamas war to promote a violent agenda on British soil or recruit supporters. The government has stepped up its concern about Tehran significantly over the past 18 months. In February, Iran was accused of being behind 15 credible threats to British-based individuals considered to be a threat to the regime. MI5 has been aware since the start of the conflict that it could have reverberations in the UK. Ken McCallum, the chief of the intelligence agency, warned earlier this month that Iran or other terror groups may step up violent activity and that Jewish groups could be targeted by neo-Nazis, Islamists and others. Any decision on whether to raise the terror threat level – which stands at “substantial” in England, Wales and Scotland – will not be made by the Cobra committee as that is a decision for the Joint Terrorism Analysis Centre. The “substantial” threat level means a terrorist attack is likely. It has been at this level since 9 February last year, when it was lowered from “severe”, meaning highly likely. The Cobra meeting took place after the UK’s most senior police officer warned that events in the Middle East were having a serious knock-on effect in Britain. Sir Mark Rowley, the Metropolitan police commissioner, said his force was facing a “particularly challenging time” after an increase in activity from Iranian-backed groups in the UK. Highlighting the scale of the risk from events in the Middle East, Rowley told Sky News on Sunday: “When you’ve got state threats from Iran, you’ve got terrorism being accelerated by the events and hate crime in communities. “For Jewish communities, it’s now about a 14-fold increase in antisemitism in London, and for Muslim communities it’s nearly threefold. So this is really precarious. In the middle of it, we’ve got these big protests.” Braverman has previously written to police officers urging them to clamp down on any attempts to use flags, songs or swastikas to harass or intimidate Jewish people. In remarks that have prompted concern from human rights lawyers and the police, she wrote: “I would encourage police to consider whether chants such as ‘From the river to the sea, Palestine will be free’ should be understood as an expression of a violent desire to see Israel erased from the world. Downing Street also sought to discourage protesters from chanting the slogan. The prime minister’s spokesperson said it was a “deeply offensive chant to many”, urging people to be “responsible for their use of language”. Nearly 100 arrests have been made in London since Hamas attacked Israel on 7 October. Rowley predicted there would be “many, many more arrests” over the coming days. On Sunday, five people were charged with offences, including displaying an illegal placard and assaulting a police officer, after the third consecutive weekend of mass pro-Palestinian demonstrations.