Britain could be more vulnerable to terrorism and organised crime if it fails to agree continued security co-operation with the European Union following Brexit, the head of the EU policing agency has warned.
Rob Wainwright, the British director of Europol for the past eight years, said ministers must get the details right in forthcoming Brexit negotiations.
"I have seen how threats of terrorism and organised crime have become much more global and how the need therefore for greater international police co-operation is absolutely essential to keeping us safe," he told Sky News.
"Mechanisms such as Europol provide an important part of the way in which the law enforcement community in Britain and other countries around Europe can discharge those responsibilities.
"It is important for Britain to get this right. It is about the security of the country. Not just the security of Britain, but of Europe."
Mr Wainwright said one option could be for the UK to become an associate member of Europol, which would give it continued access to many of its capabilities - although it would not have direct access to its database.
Ministers would also have to decide whether they wanted to continue with the European Arrest Warrant (EAW) which is bitterly opposed by many Eurosceptics but which Mr Wainwright argued had proved "hugely beneficial" to security in the EU.
"I would put the EAW as one of the most important things any country in Europe should continue to rely on in the future," he said.
"We are dealing with thousands of cases every year between these countries of very serious criminals, and even terrorists, that are identified and extradited under the terms of the warrant."
A Government spokesman said Theresa May had always been clear that one of her negotiating objectives was to continue to work with the EU on the issues of security and counter-terrorism.
"As part of the negotiations, we will discuss with the EU and its member states how best to continue cooperation on security, law enforcement and criminal justice," the spokesman said.