Britain's Brexit minister said on Monday the Northern Ireland Protocol "risks undermining" the peace accords it was meant to protect, putting the blame squarely on the European Union's "heavy-handed actions".
"The arrangements have begun to come apart even more quickly than we feared," Lord David Frost said from the Conservative Party conference in Manchester.
"Thanks to the EU's heavy-handed actions, cross-community political support for the Protocol has collapsed.
"The Protocol itself is now undermining the Belfast/Good Friday Agreement. Businesses, political parties, the institutions, and indeed all in Northern Ireland face instability and disruption," he added.
The Protocol, negotiated as part of the Brexit divorce and signed off on by both the EU and UK parliaments, sees Northern Ireland remain part of the EU's Single Market, in effect creating a de-facto border in the Irish Sea.
This is to allow freedom of movement and trade to flow unhindered between the province — part of the United Kingdom — and its southern neighbour and EU member, the Republic of Ireland. It is meant to protect the 1998 Belfast Agreement which put an end to more than 30 years of bloody sectarian violence on the island.
The UK has since called the Protocol "absurd" and called for a complete overhaul. It has also unilaterally implemented grace periods on checks which, under the Protocol, must be carried out on certain goods travelling between Northern Ireland and Great Britain.
'We need significant change'
Frost, who led Britain's Brexit negotiating team, also reiterated his threat that the UK could unilaterally call time on the deal.
He said that he had sent a set of proposals to the EU back in July and that he would soon be sending further proposals.
"We await a formal response from the EU to our proposals. But from what I hear I worry that we will not get one which enables the significant change we need," he said.
"So I urge the EU to be ambitious. It's no use tinkering around the edges. We need significant change," he argued.
He then warned that the UK "cannot wait forever" and an "agreed solution is needed soon", and that failing that Britain "will need to act, using the Article 16 safeguard mechanism, to address the impact the Protocol is having on Northern Ireland".
"That may, in the end, be the only way to protect our country - our people, our trade, our territorial integrity, the peace process, and the benefits of this great UK of which we are all part," he said.
Brussels has rejected the UK's call for the Protocol to be completely rewritten, stressing that any changes must be made within the framework of the document. But the bloc has paused its infringement's proceedings against the UK over the grace periods in a bid to appease tensions.
European Commission Vice-President and co-chair of the EU-UK Joint Committee & Partnership Council, Maroš Šefčovič, told reporters two weeks ago that the bloc aims for any outstanding issues to be resolved by the end of the year.
He said the EU had so far been "very measured, very calm, very constructive" and that in the event the UK trigger Article 16, Brussels would have to "look through all the options we have under the Withdrawal Agreement and Trade and Cooperation Agreement."