In light of the Brussels attacks which revealed a serious lapse in Belgium’s counterterrorism measures, the former head of Britain’s intelligence agency has suggested that the United Kingdom’s exit from the European Union would improve British security.

A British exit, or ‘Brexit’ from the E.U. would give the U.K. more autonomy vis-à-vis the European Convention on Human Rights, allowing for a tougher stance on border control and immigration, Sir Richard Dearlove, who served as MI6 chief from 1999-2004 wrote in British monthly, Prospect. 

The United Kingdom European Union membership referendum, also known as the EU referendum, is set to take place June 23.

The debate for and against a U.K. exit from the E.U. looks at critical topics including economic and geopolitical ramifications, but the recent string of attacks across Europe, bring to light significant national security and Islamic terror threats, ones that the E.U. is “spectacularly ill-equipped” to deal with, Nile Gardiner, Director of The Heritage Foundation’s Margaret Thatcher Center for Freedom, told The Foreign Desk.

“ISIS thrives in an environment where governments do not fully control their own borders and that’s what we are seeing within the E.U. which ISIS has exploited,” Gardiner said.

In the days since the Brussels attacks, severe intelligence failings have come to light.

Belgium ignored a warning that one of the suicide bombers in the Brussels attacks, Ibrahim el-Bakraoui, was deported from Turkey in June last year, Turkish President Tayyip Erdogan said last week.

Despite the arrest of Paris attacker Salah Abdeslam, and the reported connections between the Paris and Brussels attacks, the interrogation of Abdeslam did not help authorities foil the attacks.

“The Brussels attacks demonstrate that the E.U. open borders approach and lack of control of borders is antithetical to advancing national security in Europe,” Gardiner said.

“The way the E.U. is structured has significantly weakened the fight against ISIS and Islamic extremism, and I think we will see increased calls for the increase of border control and greater momentum for national sovereignty and self determination,” Gardiner, who foresees a high probability of the referendum passing in June, said.

Those who favor a U.K. exit, argue that being a member of the E.U., which Britain has been since 1975, undermines Parliamentary sovereignty; While those in favor, put forth the argument that the benefits of membership outweigh any loss of sovereignty.

Additional arguments for withdrawal include the U.K. having better control over immigration, possessing an advantageous position to conduct independent trade deals and being free from excessive E.U. restrictions and bureaucracy.

Supporters of Britain remaining in the E.U. also warn that an exit will decrease U.K. authority over foreign affairs, increase national security risks by limiting access to shared European criminal databases and create trade barriers between the U.K and the E.U.

In January 2013, David Cameron said should the Conservatives be victorious with a parliamentary majority in the 2015 general election, the government would then discuss more advantageous provisions for maintaining membership within the E.U. before holding a referendum on whether to exit altogether.

Leaders in Germany and France, who have not been pleased with talk of Britain’s potential exit, have warned that the U.K. would not be able to dictate its own membership terms, while at the same time supported their stay within the E.U.

The Obama administration has repeatedly warned against a U.K exit from the E.U., arguing that it would diminish the British “voice” in the Union.

President Barack Obama has announced that he will visit London in April to advocate against a U.K. departure from the E.U., which has angered some British legislators.