Being in Europe, working together and sharing intelligence with other EU countries, is essential to Britain's national security, six former Home Secretaries have written in a letter to the Times.
"Campaigners for Britain to leave the EU are wrong. Horrific events in Paris underline that Europe is essential for British national security.
By sharing intelligence, pooling resources and working together, European countries add value to each others’ efforts to tackle terrorism. We become more than the sum of our parts.
This is embodied in the European Arrest Warrant, which speeds arrangements to deport criminal suspects.
After the 1995 Paris Metro bombing one suspect, Rashid Ramda, was held in British custody for seven-and-a-half years before he could be extradited to Paris and convicted. Now, thanks to the EAW, there is no such wait. A man linked to the Charlie Hebdo shootings was found in Bulgaria and immediately returned to Paris.
Since 2010 Britain has removed over 5,000 criminal suspects to EU countries under the EAW. 675 have been returned to face British justice, as was a terrorist who attacked London in 2005.
Just this month British Counter-terrorist police arrested four men accused of plotting to kidnap British diplomats as part of a Europe-wide operation led by Italian Police.
All British governments have been united in the UK keeping its own border controls, outside Schengen. Schengen itself does need reforms, not least heavily to strengthen its Mediterranean borders. We can influence that far better from inside the EU than outside.
The overriding priority for any British Government is to keep Britain safe. As the threat level rises we know that, without European cooperation, we would be more at risk."
Rt Hon. Kenneth Clarke CH QC MP (1992-1993)
Rt Hon. Jack Straw (1997-2001)
Rt Hon. Lord Blunkett (2001-2004)
Rt Hon. Charles Clarke (2004-2006)
Rt Hon. Jacqui Smith (2007-2009)
Rt Hon. Alan Johnson MP (2009-2010)