LONDON (Reuters) - Britain proposed a new post-Brexit security treaty with the European Union on Monday, seeking to maintain and intensify cooperation to thwart  ever-growing and increasingly cross-border threats . In its sixth policy paper setting out Britain s vision for ties with the EU after it quits the bloc in March 2019, the government said it wanted to keep the benefits of EU security cooperation, arguing it was in both parties  interests to do so. The proposal comes days after a blast on a packed commuter underground train injured 30 people in west London, Britain s fifth major attack this year.   We already have a deep level of collaboration with the EU on security matters and it is in both our interests to find ways to maintain it,  Brexit minister David Davis said in a statement.  A new security treaty with the EU would be underpinned by our shared principles, and should make sure our partnership has the agility to respond to the ever-changing threats we face.  The paper said an entirely new form of agreement on security was necessary because there was no satisfactory precedent for security cooperation between the EU and non-EU states, and that relying on existing models would diminish British and EU defenses. Britain has published a series of  future partnership  policy papers to try to nudge talks with the EU forward, after they have stalled over the divorce settlement, especially over the so-called Brexit bill. Security cooperation is seen by government officials as one of their strongest arguments to gain leverage in the complicated talks to unravel more than 40 years of union. Seeking to ram that point home, Monday s paper simultaneously stressed Britain s importance to EU security, and the need for continued cooperation to respond to future threats as they evolve. Interior minister Amber Rudd said Britain was one of the leading EU contributors to a range of measures, such as data and evidence sharing, extradition measures and to the EU s police agency Europol.  Recent events in the UK and across Europe have shown the criminal and terrorist threats we face are varied and increasingly international. The long-standing collaboration we have with our European partners allows us to jointly address these threats and keep our citizens safe,  she said.  As we prepare to leave the EU it is therefore vital that we agree a new way to ensure continued security, law enforcement and criminal justice cooperation,  Rudd said. The document did not rule out Britain seeking membership of police agency Europol and other bodies, or using the European Arrest Warrant which provides fast-track extradition. Its focus, however, was finding a way to keep the  operational capabilities  provided by those instruments. 
Nothing should change, says Britain in bid for post-Brexit security pact