Brexit minister Lord Frost has claimed the European Union has behaved "without regard to the huge political, economic and identity sensitivities" in Northern Ireland.
His comments were published in the foreword to a new paper for the Policy Exchange think tank that sets out how negotiations in the Brexit process have been hindered by decisions made in 2017.
It comes after the UK and the EU put forward proposals to address the dispute over the protocol, in which he negotiated.
The protocol is a key part of the Brexit deal struck between London and Brussels and is designed to avoid a hard border on the island of Ireland.
Northern Ireland is effectively kept in the single market due to the terms of the protocol.
This creates a border down the Irish Sea between the region and the rest of Great Britain - which has angered unionists and hit the UK's internal market.
"We must return to the protocol and deliver a more robust, and more balanced, outcome than we could in 2019," Lord Frost said.
He argues that a 2017 EU-UK joint report, which set the terms for the Brexit process, was a result of the UK failing to make "the necessary mental shift from being a member of the EU to negotiating exit from the EU".
Lord Frost, who was elevated to the House of Lords as a life peer last year, also claimed it was a result of the "extreme weakness" of the UK government after the June 2017 election.
The paper, titled The Northern Ireland Protocol: The Origins of the Current Crisis, by Roderick Crawford, chronologically details Brexit negotiations and what went wrong in 2017.
It argues that commitments in the 2017 joint report, particularly on the Irish border, were "a diplomatic triumph for Ireland and the (European) Commission" but "failing to secure adequate reciprocal concessions was a staggering failure for the UK".
Its author, Mr Crawford, claims the report led to a flawed February 2018 draft withdrawal agreement and the subsequent November 2018 Withdrawal Agreement.
That ultimately resulted in the fall of Theresa May's government in 2019, the paper claims, and "tied the hands" of Boris Johnson's new government as it renegotiated the terms of Brexit.
Lord Frost also warns that enforcement of the Northern Ireland Protocol "has begun to damage" the Good Friday Agreement.
He also says he considered resigning in December 2017 after reading the terms of the joint report and realising "a crucial pass had been sold".
Last week, Lord Frost said the EU's current proposals to reform the Northern Ireland Protocol "don't go far enough" - as he set a December deadline for the two sides to find a solution.