He suggested the issue had "been assumed on all sides to be readily soluble"
Boris Johnson has said a 'fog of self-doubt has descended' over the British government's Brexit plans, and claims the Irish border has 'dominated the debate'.
The former foreign secretary resigned from his position last week in protest against the Brexit proposals agreed by Theresa May's cabinet at Chequers earlier this month.
In a personal statement in the House of Commons this afternoon, Mr Johnson praised the British Prime Minister for her 'courage and resilience', and also noted her 'great clarity' during a key Brexit speech in January 2017.
However, he argued: "In the 18 months that have followed, it is as though a fog of self-doubt has descended.
"We dithered. We burned through negotiating capital. We agreed to hand over a £40 billion exit fee, with no discussion of our future economic agreement."
He added: "Worst of all, we allowed the question of the Northern Irish border, which had hitherto been assumed on all sides to be readily soluble, to become so politically charged as to dominate the debate.
"No one wants a hard border. You couldn't construct one if you tried. But there certainly can be different rules north and south of the border to reflect the fact that there are two different jurisdictions. In fact there already are."
Read my personal statement to the House of Commons this afternoon. pic.twitter.com/Zy6klFWQsr— Boris Johnson (@BorisJohnson) July 18, 2018
He suggested there can be 'checks away from the border' and 'technical solutions' to address the issue, but claims such proposals were 'never even properly examined'.
He also claimed that technical solutions became 'taboo even to discuss' after a backstop agreement to avoid a hard border was reached last December.
Insisting it is "not too late to save Brexit", Mr Johnson concluded: "If the Prime Minister can fix [the] vision once again before us then I believe she can deliver a great Brexit for Britain."
His comments come amid the ongoing political turmoil in Westminster, which has seen several high-profile resignations and the British government only narrowly winning a series of key votes on Brexit.
Theresa May is set to visit Northern Ireland tomorrow to 'hear views from businesses on the border'.
Meanwhile, the Irish Cabinet is meeting in Kerry today to discuss contingency plans for the UK's withdrawal.
The Government here still thinks a no deal Brexit is highly unlikely, but they have been examining plans looking at all the possible scenarios that may result from the UK's exit from the European Union.
Tánaiste Simon Coveney said people shouldn't be panicked by the tensions in Westminster, and stressed the Government is not preparing for a hard border.
He observed: "What has already been agreed on the Irish border is that Britain has ruled out border infrastructure on the island of Ireland. We have insisted on that also. The EU side has also insisted on it."
He added: "While we haven't been talking a lot about contingency planning to date - for good reason actually, in the context of a negotiating strategy - there has been an enormous amount of work going on for the best part of a year now, across multiple Government department and agencies, to make sure we are prepared for whatever outcome emerges from Brexit."
Negotiations are continuing between the EU and UK, ahead of the October deadline for a deal to be reached before the UK's official exit in March 2019.