The head of Britain's spy agency says the European Union must work together to counter Islamic militants and Russia.
In the first public speech outside Britain by a serving head of MI5, Andrew Parker told European spy chiefs Islamic State militants are plotting "devastating and more complex attacks".
And Russia, he says is trying to carry out "aggressive and pernicious actions" with its military and intelligence services.
Britain suffered four deadly militant attacks last year - a suicide bombing at a Manchester pop concert and an attack on London Bridge.
Parker stressed the rate of planned attacks showed no signs of abating.
"In the UK alone, since the Westminster attack in March last year with the police we have thwarted a further 12 Islamist terror plots 12 occasions where we have good reason to believe a terrorist attack would otherwise have taken place in our country," he said.
Britain wants a new security pact with the EU to ensure continued access to secrets from major EU countries after it leaves the bloc in 2019.