Rob Wainwright, the director of the European law enforcement agency, has urged the Government to push for a strong future relationship with Europol in the Brexit negotiations.
A former MI5 intelligence analyst, Mr Wainwright is scheduled to be the last British director of Europol, with Brexit set to mean the UK stops being a full member.
He told Sky News: “I have seen how threats of terrorism and organised crime have become more global and the need for greater international police cooperation is absolutely essential to keep us safe.
"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."
He added: "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.
Rob Wainwright has said Brexit could leave the UK more at risk of an attack
"It is a big issue and we need to get the details right of what those arrangements could be."
Mr Wainwright also pushed for the UK to continue its involvement in procedures such as the European Arrest Warrant.
He said: “I would put the EAW as one of the most important things any country in Europe should continue to rely on in the future.
"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.”
In response, Ukip’s home affairs spokeswoman Jane Collins said the 49-year-old civil servant was still fighting the referendum campaign.
She said: “I am sure that the UK government will secure some kind of intelligence sharing but what people should be aware is that the UK is part of a superior organisation called Five Eyes, a multilateral agreement with Australia, Canada, New Zealand and the USA where we share signals intelligence.
Rob Wainwright has called for a deal with the EU that secures future security cooperation
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If you are an EU national, you do not need to show your national ID card or passport when you are travelling from one border-free Schengen EU country to another. The Schengen Area is an area comprising 26 European states that have officially abolished passport and any other type of border control at their mutual borders.
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They need us more than we need them
"The fact is we give Europol more intelligence than they give us and they are not invited to be part of 5 Eyes because of concerns about leaking.
"And what is more important is a properly funded security services and military and secure borders.
"We will be a more secure nation if we don't have free movement of terrorists and weapons which Schengen has brought right to our doorstep."
Lord Carlile, a former independent reviewer of terrorism, said a reduction in cooperation between the EU and the UK post-Brexit would actually put the EU at greater risk.
He said it was “inconceivable” the UK would not agree a deal which secured a high level of cooperation over international security.
Lord Carlile said the EU needed the UK at lot more than the UK needed the EU in regards to security
“The British police and the British intelligence services provide a disproportionally high amount of the information which helps European intelligence agencies and police to prevent and detect terrorism.
“They need us more than we need them.”
Earlier this month Scotland’s senior prosecutor said the country could be at risk of becoming a safe haven for criminals.
Lord Advocate James Wolffe said it was vital Britain retail current levels of justice and law cooperation.
He said: "One of the risks if we had, for example, no robust legal arrangements for the extradition of individuals wanted for trial in other countries, is that we would become a safe haven for criminals.
"Equally, if we were unable to extradite to Scotland people who we wish to prosecute then plainly our criminal justice system would be prejudiced. If we were not members of the EU the extradition process would be significantly more cumbersome, both slower and more difficult to operate.
"Ultimately, it will be a matter for negotiation what arrangements are put in place, but from my perspective as the prosecutor of crime in Scotland, it's hugely important that the right choices are made and the right priority is given to those particular arrangements."