In a speech in Munich, the Prime Minister will warn that “rigid institutional restrictions” and “deep-seated ideology” must not be allowed to jeopardise the safety of citizens.
She will set out plans for a new treaty between the UK and the European Union to enshrine security cooperation and warn a reluctance to agree a new type of partnership would have “damaging” consequences.
Mrs May will say: “The challenge for all of us today is finding the way to work together, through a deep and special partnership between the UK and the EU, to retain the co-operation that we have built and go further in meeting the evolving threats we face together.
“This cannot be a time when any of us allow competition between partners, rigid institutional restrictions or deep-seated ideology to inhibit our cooperation and jeopardise the security of our citizens.
“We must do whatever is most practical and pragmatic in ensuring our collective security.”
It comes after the head of MI6 joined with his French and German counterparts to appeal for continued intelligence sharing after Brexit.
In a rare joint statement after meeting at the Munich Security Conference, Alex Younger, BND boss Bruno Kahl and French DGSE chief Bernard Emie said cooperation between EU agencies was “indispensable”.
The Prime Minister again insisted Britain’s commitment to maintaining European security is “unconditional” when she visited Berlin for talks with German Chancellor Angela Merkel on Friday.
But as well as facing tricky negotiations in Brussels to secure a strong agreement, the PM is also under pressure from Brexiteers in her party who are fundamentally opposed to the European Court of Justice having any oversight role in a settlement, such as in relation to the European arrest warrant.
Mrs May wants the Supreme Court to have the final say over challenges to warrants issued in the UK.
She will highlight major cases where the UK and the rest of the EU have worked together to tackle terrorists and people smugglers and will insist it is in the interest of both sides to agree a strong security deal.
“To make this happen will require real political will on both sides,” she will say in the speech titled Road to Brexit: A Security Partnership.
“I recognise there is no existing security agreement between the EU and a third country that captures the full depth and breadth of our existing relationship.
“But there is precedent for comprehensive, strategic relationships between the EU and third countries in other fields, such as trade. And there is no legal or operational reason why such an agreement could not be reached in the area of internal security.
“However, if the priority in the negotiations becomes avoiding any kind of new cooperation with a country outside the EU, then this political doctrine and ideology will have damaging real world consequences for the security of all our people, in the UK and the EU. As leaders, we cannot let that happen.”
The speech is the second of six key addresses by the PM and senior Cabinet ministers mapping out the Government’s plans for Brexit.
Mrs May will tell the security conference the proposed new treaty must be drawn up to allow the partnership to respond swiftly to the world of rapidly evolving threats.
She will warn “nothing must get in the way” of Britain and the EU “helping each other in every hour of every day to keep our people safe”.
“Those who threaten our security would like nothing more than to see us fractured,” Mrs May will add.
“They would like nothing more than to see us put debates about mechanisms and means ahead of doing what is most practical and effective in keeping our people safe.
“So let our message ring out loud and clear today: we will not let that happen. We will keep our people safe, now and in the years to come.”