Jeffrey Donaldson has urged the European Union to put Northern Ireland's interests first "rather than acting out of selfish interest".
The Democratic Unionist Party leader was speaking after No 10 said "limited" progress had been made in talks between Brexit minister David Frost and European Commission vice-president Maros Sefcovic in Brussels on Friday.
Mr Sefcovic said he had been disappointed in the UK’s unwillingness to compromise.
Mr Frost said Article 16, which would allow parts of the deal to be suspended, was “very much on the table”, while Mr Sefcovic said invoking the protocol would have “serious consequences”.
Mr Donaldson slammed that comment by Mr Sefcovic as “intemperate, ill-judged and very ill-advised”.
"They [the EU] ought to recognise that the protocol and its Irish Sea Border is causing economic harm and undermining stability in Northern Ireland, " he said.
“These negotiations cannot become a process to excuse away the real problems of the protocol nor is it acceptable for those with EU interests to now claim that a legal mechanism within the protocol – namely Article 16 cannot and should never be used.
"Indeed, I would remind those who claim that it is against the spirit of the Belfast Agreement to invoke Article 16, in circumstances where it is done to commence a process of re-establishing NI's place in the UK internal market, that a border down the Irish Sea is the real and damaging breach of the 98 Agreement.
“The Government set out a reasonable position in its command paper and our view remains unchanged that unless the Irish Sea border goes then it will not be business as usual in Northern Ireland.
“It is time the interests of NI were put first by the EU rather than behaving in a manner which has brought us to the brink.”
Meanwhile, Sinn Féin MLA Declan Kearney slammed "threats and rhetoric" from Mr Frost as "reckless and at odds with where widespread public and political opinion is on the protocol in the North, and across the island".
“The protocol recognises the special status of this island. It prevents a hard border, safeguards jobs and the all-Ireland economy, and protects the Good Friday [Belfast] Agreement. Significantly it also provides unique dual-market access for local businesses, manufacturers and agri-food sector,” he said.
“The Tories and the DUP must not be allowed to undermine the opportunities available to our businesses, manufacturers and farmers to create jobs and attract investment.
“An urgent meeting of the Joint Committee which was set up to manage the implementation of the protocol should now be convened.
“It is essential that this British government sets aside its destructive ideological agenda and starts demonstrating a serious commitment to find workable solutions which further reduce the potential for trade friction, and give the certainty to businesses, their workers and families which they deserve.” – PA
