Boris Johnson has criticised Rishi Sunak's new Brexit deal for Northern Ireland, arguing it is "not about the UK taking back control" and suggesting he will not vote for the plan.
The Prime Minister's main Conservative Party rival said he would find it "very difficult" to vote for the Windsor Framework agreement on the Northern Ireland Protocol impasse.
Mr Johnson said he hopes the DUP restores Stormont but raised concerns about the new deal between the UK and European Union on Irish Sea trading arrangements.
Read more: DUP issues statement after Ian Paisley says Windsor Framework does not meet party's seven tests
In a speech in Westminster, he said: "I'm conscious I'm not going to be thanked for saying this, but I think it is my job to do so, we must be clear about what is really going on here.
"This is not about the UK taking back control and although there are easements this is really a version of the solution that was being offered last year to Liz Truss when she was foreign secretary.
"This is the EU graciously unbending to allow us to do what we want to do in our own country, not by our laws, but by theirs."
Mr Johnson called for his divisive Westminster bill to override the protocol, which the EU argued would have breached international law, to be restored if the new deal does not work.
He said: "I'm going to find it very difficult to vote for something like this myself, because I believed we should’ve done something very different. No matter how much plaster came off the ceiling in Brussels.
"I hope that it will work and I also hope that if it doesn't work we will have the guts to employ that Bill again, because I have no doubt at all that that is what brought the EU to negotiate seriously."
Mr Johnson conceded he made mistakes in agreeing the Northern Ireland Protocol, which prompted the DUP to block Stormont in protest against new Irish Sea trade barriers.
"I thought those checks would not be onerous since there isn't that much stuff that falls into that category; most of the goods stay in Northern Ireland," he said.
Muttering, the former Prime Minister added: "It's all my fault, I fully accept responsibility."
The DUP has been blocking Stormont power-sharing in protest against the protocol, which angered unionists for creating new barriers on trade from Great Britain to Northern Ireland.
Announced this week, the new Windsor Framework includes a new red and green-lane system for trade and an "emergency brake" for Stormont on future changes to EU goods rules applying to the region.
Brexit hardliners in the Conservative European Research Group (ERG) are analysing the deal to see if they will support it, while the DUP is having its own debate.
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