Sir John and Mr Blair said: “It puts the Good Friday Agreement at risk, because it negates the predictability, political stability and legal clarity that are integral to the delicate balance between the north and south of Ireland that is at the core of the peace process.
“This has wide-ranging ramifications. It will not only make negotiation with the EU more difficult, but also any trade negotiations with other nations, including the United States.
“Once trust is undermined, distrust becomes prevalent.
“We both opposed Brexit. We both accept it is now happening.
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