Europe faces a "populist uprising" if it is unable to show people it can control the migrant crisis, former MI6 head Sir Richard Dearlove has said.
He was speaking on the BBC's World on the Move day on migration issues.
Sir Richard also warned against offering visa-free travel to Turkish nationals, describing the move as like storing gasoline near a fire.
Earlier, UN special envoy Angelina Jolie Pitt warned the humanitarian system for refugees was breaking down.
She spoke of a "fear of migration" and a "race to the bottom" as countries competed to be the toughest to protect themselves.
BBC News World On The Move is a day of coverage dedicated to migration, and the effect it is having on our world.
A range of speakers, including the UNHCR's special envoy Angelina Jolie Pitt, and former British secret intelligence chief Sir Richard Dearlove, have been setting out the most important new ideas shaping our thinking on economic development, security and humanitarian assistance.