Priti Patel last night vowed to take back control of our borders and make Britain more secure.
The Home Secretary said the trade deal struck with the EU, which includes an agreement on security cooperation, would allow for 'firmer' checks on entry to the country.
But, according to a leaked copy of the accord, the UK has agreed not to water down or scrap European human rights laws that can be exploited by criminals.
Priti Patel last night vowed to take back control of our borders and make Britain more secure
It says Brussels can suspend cooperation if Britain 'denounces' – code for fails to uphold – the European Convention on Human Rights. Britain has ruled out quitting the ECHR but Miss Patel has vowed to stop foreign offenders using its provisions to dodge deportation.
In October it emerged that she wants to restrict article 3 of the convention, which states no one should be subject to torture or inhuman or degrading treatment.
The EU-UK security deal potentially shuts down her options.
It also means Britain will have to follow European human rights laws if it wants the security deal to continue. The laws are a separate legal system that sits outside the EU.
A senior Brussels negotiator said: 'In our negotiation we wanted it to be clear that cooperation in this matter will be subject to the condition that the UK will continue to adhere to this convention, and that we will be able to invoke this convention in the international courts in the UK. So, this is now clearly stated in the agreement.'
The UK will keep some access to key European agencies and databases to help fight cross-border crime and terrorism.
However, Brussels has warned that 'direct, real-time access' to sensitive information will cease.
Miss Patel said: 'I'm immensely proud of the comprehensive package of capabilities we've agreed with the EU'
Police and security chiefs have expressed concern about Britain leaving bodies such as Europol, the EU's key security agency.
But Miss Patel said: 'I'm immensely proud of the comprehensive package of capabilities we've agreed with the EU.
'It means both sides have effective tools to tackle serious crime and terrorism, protecting the public and bringing criminals to justice.'
Officials say a string of tougher measures can be introduced next year.
These include police being able to detain foreign fugitives without having to apply for a UK arrest warrant first, potentially bringing them to justice faster.
The UK will lose full access to other systems such as the EU's Schengen Information System II, which has alerts about flagged individuals.
UK police checked it 603million times last year. The deal also means the UK will come out of the European Arrest Warrant system.
Streamlined extradition arrangements have been agreed instead.