Senior law enforcement leaders have written to MPs warning of a “major operational impact” from the loss of EU databases and mechanisms, even if a security deal is struck before 31 December.
But government ministers have evaded questions on the looming downgrade, insisting that the UK will remain a “global leader on security”.
In a letter seen exclusively by The Independent, Conor McGinn, Labour’s shadow security minister, demanded a response to a warning from the National Police Chiefs’ Council (NPCC) that “even with contingencies in place, fallback systems will be slower, provide less visibility of information/intelligence and make joined-up working with European partners more cumbersome”.
He said the security minister, James Brokenshire, had “declined to directly answer” whether he agreed with the assessment three times at a committee hearing on Wednesday.
“These are clearly very serious concerns to be raised by one of the country’s most senior police officers,” the letter added.
“The government has had a significant amount of time to put in place vital reciprocal security arrangements. So it is deeply concerning that as deadlines fast approach senior police officers are concerned about such critical tools.”
Mr McGinn asked what assessment had been made of the scenario British law enforcement will find themselves in on 1 January, and what additional planning was being undertaken in light of “serious warnings regarding the efficacy of contingency plans”.
He said the government must answer the questions urgently and provide “assurances that our law enforcement agencies and security services will not be undermined in undertaking their vital work”.
In a letter to parliament’s Home Affairs Committee that was published on Tuesday, NPCC chair Martin Hewitt said police leaders had been “quite clear” on the need to retain EU tools since the 2016 EU referendum.
“In both a negotiated outcome and non-negotiated scenario, the alternative measures are less automated and more unwieldy to use,” he added, warning of a “major operational impact” in January.
The National Crime Agency (NCA) said that even if a security deal is struck in the coming weeks, access will still be lost to vital databases and legal mechanisms.
During a terse exchange on post-Brexit security with Theresa May in the House of Commons last month, the Cabinet Office minister Michael Gove claimed that the government “can intensify the security that we give to the British people”.
But the NCA appeared to dismiss that claim, writing: “Whilst new powers at the border, such as the provision of advance data on EU goods, will have a positive impact on Border Force’s targeting ability, this may not fully offset the overall operational deficit.”
The NPCC and NCA said British authorities would no longer be able to use the Schengen Information System (SIS II), which contains 4.6 million UK alerts relating to people and objects and is integrated with Britain’s Police National Computer.
Its replacement will be Interpol notices and diffusions, which must be searched manually and currently contain far less information relevant to the UK.
The NCA said the UK would also be cut out of the European Arrest Warrant system because it was “not seeking to participate as part of the future relationship” but seeking fast-track extradition agreements instead.
Britain also faces losing access to the Prüm database for DNA, fingerprints and vehicle registration data, and the European Criminal Records Information System, on which the UK is the most active member state.
The NCA warned that the UK would have less access to information on terrorists and gangsters trying to enter the country if Britain is removed from the Passenger Name Records database.
Britain’s participation in Europol, an umbrella body bringing together EU enforcement partners, is still under discussion.
“The safety and security of the British people should have been a top priority for the government in these negotiations,” Mr McGinn said.
“Instead, as deadlines fast approach, respected policing and security figures have raised serious concerns that continuing uncertainty – or worse still, an end to security cooperation and data sharing – will hamper the UK’s fight against crime and terrorism.
“Mr Brokenshire needs to urgently provide assurances and clarity to our law enforcement agencies and the British public.”
The government said it was working closely with police and criminal justice agencies to be ready for possible outcomes at the end of the transition period.
A spokesperson added: “The safety and security of our citizens is our top priority, and the UK will continue to be a global leader on security and one of the safest countries in the world.
“We are focused on reaching an agreement with the EU and there is a good degree of convergence in what the UK and EU are seeking to negotiate in terms of operational capabilities.
“In the event that it is not possible to reach an agreement, we have well-developed and well-rehearsed plans in place.”