Richard Dearlove, who was head of Britain's Secret Intelligence Service, or MI6, from 1999 to 2004, made the comments Monday at an event for the BBC's World on the Move day, in which the British broadcaster focused its coverage on migration issues.
Speaking on how the migrant crisis has affected politics and security in Europe, he said that for the European Union "to offer visa-free access to 75 million Turks to stem the flow of migrants across the Aegean seems perverse, like storing gasoline next to the fire we're trying to extinguish."
The promise of visa-free travel for Turks through the European Union
has been floated as part of a deal between the 28-member bloc and Turkey to secure Ankara's help in stemming the flow of migrants passing through its territory
and on into Europe.
European leaders negotiated the deal in March to tackle the crisis
, after more than a million irregular migrants, many fleeing violence in the Middle East and Afghanistan, entered Europe's borders last year.
Under the terms of the so-called "one-for-one" deal, people who cross into Europe illegally are being sent back to Turkey, and for every Syrian sent back to Turkey, a vetted Syrian refugee will go from Turkey to be resettled in Europe.
In return, the EU will give Turkey billions in funding to help it provide for the migrants within its borders, and grant various political concessions, including the right for Turks to travel through Europe without a visa.
The proposal would see Turkey's 75 million citizens gain the right to enter the European Union's Schengen zone for up to 90 days at a time with biometric passports.
But talks over the deal have stalled over Turkey's refusal to reform its anti-terror laws.
Turkey has been trying to become a member of the EU since 1987, when it was still called the European Economic Community.
Ex-spy chief: Marshall Plan for migration needed
Rather than granting visa-free travel to millions of Turks, Dearlove said that measures such as the EU's allocation of 1.8 billion euros to tackle the issues in Africa driving people to become migrants in Europe make "much more sense."
"But this is not nearly enough money to embrace the vastness of the problem," he said.
"How do you persuade the millions of people not to set out towards Europe in search of employment and a better life?"
He said that "probably the only answer" is a "massive European response" akin to the Marshall Plan, in which the U.S. government spent billions to help rebuild shattered European economies after World War II.
Also crucial is a "much more aggressive" maritime operation along the Libyan coastline.
He described the European response to the migrant crisis as "hesitant and irresolute, complicated by the differing reaction of member states and the extent to which their national interests are affected."