THE Northern Ireland Protocol was "arguably one of the worst pieces of negotiation that we have seen in recent history", former British Prime Minister Sir John Major has said.
In a scathing attack on Boris Johnson, Sir John also said "it does help if you sign treaties if you understand them before you sign them".
Speaking at an Institute for Government event in London yesterday, he also claimed that the Protocol was "causing an enormous amount of trouble".
During his speech, the former Conservative leader warned that attempts to excuse the breaking of lockdown laws by No 10 was undermining trust in government and politics.
A long-standing critic of Mr Johnson, Sir John said the prime minister should resign from office if he has broken lockdown laws over parties held in Downing Street as he accused the British government of feeling it "need not obey the rules".
Sir John, who was prime minister from 1990 to 1997, was asked by the media if he thought Mr Johnson had lied about the implications of Brexit.
"You may remember that in 2016, Tony Blair and I went together, an unlikely duo you may think, went together to Northern Ireland to warn of the dangers to Northern Ireland of the protocol and to the peace process," he said.
"We warned then, and as I recall were not too gently told by the then secretary of state for Northern Ireland and the leader of the DUP that neither Mr Blair or I knew anything about Ireland and we should pipe down.
"Well it looks as though we might have known a little about it from the difficulties that exist at the present time.
"The Northern Ireland Protocol was arguably one of the worst pieces of negotiation that we have seen in recent history, it is causing an enormous amount of trouble.
"Whether anyone deliberately misled about that I can't say, certainly they were mistaken.
"But it does help if you sign treaties if you understand them before you sign them."
Sir John's comments come a week after the DUP's Paul Givan resigned as First Minister as part of his party's protest over the Protocol.
Unionists have argued that Northern Ireland's place in the UK is being undermined by the protocol as it is being treated differently from Great Britain.
DUP MP Ian Paisley also told Mr Johnson in the House of Commons on Wednesday that the Protocol has "zero support from unionists".
