Schools have been told to stock up on longer shelf life products in preparation for a no-deal Brexit, as police chiefs warned that such an outcome would damage their ability to fight crime. Department for Education (DfE) guidance published on Tuesday urged schools to prepare for what was described as “possible changes to their food supply chain” from 1 January “so they can minimise the effect on pupils and young people in their care”. Stressing that schools would still be responsible for meeting children’s dietary requirements, the guidance said necessary changes might include “varying the timing and number of deliveries to allow for transport delays” and “ordering longer shelf life products during this period, such as frozen foods or foods that can be safely stored at room temperature”. Unions expressed concern with Paul Whiteman, general secretary of school leaders’ union NAHT warning: “Let’s be frank: there’s almost nothing that any school can meaningfully do to mitigate the effects of Brexit, as they have no control over what will happen after 1 January.” “So it is entirely wrong for the government to offload responsibility for a successful Brexit outcome onto schools and other public services.” The guidance came as a new letter from police chiefs warned that a no-deal Brexit would cause “major” operational damage to their ability to fight crime and terrorism. Crucial tools used millions of times a year would be lost, with their replacements slower and less effective, the letter from police chiefs warned. The letter from Martin Hewitt, the chair of the National Police Chiefs’ Council, was requested by MPs on the Commons home affairs committee. It puts more pressure on the government as Brexit talks reach a crucial stage, with the UK due to crash out on 31 December if no deal is reached. The letter lists key crime-fighting tools affected or lost by the UK’s exit from the EU, their possible replacements under no deal and how effective police chiefs believe they will be. Hewitt wrote: “As an overarching principle, the loss of some or all of the tools will mean that, even with contingencies in place, the fallback systems will be slower, provide less visibility of information/intelligence and make joined-up working with European partners more cumbersome.” In a section on the Schengen Information System, known as SIS II, which allows police forces across the EU to swap names of people they are looking for, Hewitt wrote: “This loss will have a major operational impact.” He continued: “SIS II is currently aligned to national systems meaning that anyone circulated as wanted or missing automatically can be seen by 27 EU member states and vice versa.” Police have previously said the system was used more than 500m times in 2018. It is estimated nearly one in five suspects taken into police custody areas in the UK are foreign nationals, rising to more than a quarter in London. He said the loss of the European arrest warrant would lead to a worse replacement with some EU member states, namely Germany, Austria and Slovenia, refusing to extradite their own citizens. Passenger name records to help screen those coming through UK airports will also be lost. The police chiefs said this “would have a major impact for CT [counter-terrorism] and serious and organised crime related matters”. The home affairs committee released two letters on Tuesday, the one from Hewitt and one from the National Crime Agency. Yvette Cooper MP, the committee chair, said the letters revealed important details for the first time and was worrying. “These are extremely serious and frankly very troubling letters from the country’s senior police officers who are in charge of law enforcement preparation for January 1 about the security downgrade the UK will face if there is no negotiated outcome in the next few weeks. “They make clear that without a negotiated outcome the UK authorities will lose the ability to use a wide range of law enforcement tools with ‘a major operational impact’ on policing and security.” Hewitt said police were working hard to minimise the damage and the government had provided some extra money. He wrote: “We have planned for both a negotiated outcome (NO) and non-negotiated outcome (NNO).”