Brexit could lead to fragmentation of EU, instability, ex-MI5, MI6 heads say

The ex-heads of MI5 and MI6 told the Sunday Times that the UK leaving the European Union might hamper anti-terrorism efforts and have a profound negative impact on the EU and, in time, on Britain itself.

John Sawers, the foreign intelligence service's chief spook until 2014 and Jonathan Evans, who headed MI5 until three years ago, warned of the potential damage that might be done to intelligence gathering by Britain and its neighbours.

"Counterterrorism is a team game, and the EU is the best framework available — no country can succeed on its own," they said.

"If the UK were to withdraw from the EU, the destabilising effect on the EU itself — already beset with economic difficulties, the migration crisis and a resurgent Russia — could be profound," they added.

"Those who are enemies of democracy would rejoice. In our judgement, there is a real risk that such a destabilisation could, in time, lead to the fragmentation of the EU and the return of instability on the continent."

Their remarks stood in contrast with those of another ex-intelligence chief, Richard Dearlove, who on 24 March said Brexit would do little harm to the country's national security, indeed in his opinion quite the opposite might be true.

"Whether one is an enthusiastic European or not, the truth about Brexit from a national security perspective is that the cost to Britain would be low," Dearlove sain in an article published in Prospect magazine.

"Brexit would bring two potentially important security gains: the ability to dump the European Convention on Human Rights...and, more importantly, greater control over immigration from the European Union."