A government’s negotiator for the Belfast Agreement has accused Boris Johnson of “playing games” with the peace process.
Jonathan Powell was the government’s chief negotiator for NI from 1997 until 2007.
Unionists have expressed concerns about Mr Johnson’s Brexit deal splitting NI from the rest of the UK.
Mr Powell says the prime minister is dealing with Northern Ireland from a “position of ignorance”.
He told BBC’s The View: “It’s so unwise to play games with this. This peace process is a seesaw, if you jump on one end, the other end’s going to go flying in the air. A sensible government should be balancing that.”
Mr Powell added: “I can understand why people feel glad the DUP has been shafted after them making this close alliance.
“But that’s an unwise attitude for the long term. This peace process has two parties at the centre, and if either of their identities are attacked we’ll have difficulties sustaining that.”
He said Mr Johnson had not understood what he had agreed to for Northern Ireland in his Brexit deal and that hardly anyone in the government had any “real knowledge” of the situation.
As long as Brexit is “hanging over people, it will be very hard to get the institutions back up and running, because it undermines the Good Friday Agreement and the peace process” he added.
“It doesn’t have to be terminal if people come to their senses - it can be saved but it is very worrying.”