DUP leader Arlene Foster has accused the Prime Minister of "demeaning the strength of this great nation" in her "weak" approach to the Brexit talks.
Mrs Foster said the decision to leave the EU was not the problem but rather Theresa May's "ham-fisted" approach to the talks and accused the Prime Minister of trying to force people into backing her Brexit deal.
The MLA made the comments ahead of a meeting with chief EU Brexit negotiator Michel Barnier and with MEP Diane Dodds and Conservative MPs Ian Duncan Smith and Owen Paterson.
“This is a useful opportunity to once again set out why we oppose the Withdrawal Agreement and urge the EU’s Chief Negotiator to acknowledge the concerns of those we represent in Northern Ireland by making the changes outlined by Parliament on 29 January," she said.
In parliament on January 29 MPs backed a backbench amendment tabled by Sir Graham Brady. The amendment demanded the backstop by replaced by unspecified "alternative arrangements".
However, the EU and the Prime Minister have said there can be no change to the withdrawal agreement and it will form part of any deal.
Mrs Foster added: "We want to see a sensible deal which works for every part of the United Kingdom and respects the referendum result. However, we cannot settle for a deal which would undermine the economic and constitutional integrity of the United Kingdom.
"The European Union has spoken much about protecting the peace process and the Belfast Agreement but has consistently ignored the views of unionists who do not want a new border erected between Northern Ireland the rest of the United Kingdom."
That is a weak approach and demeans the strength of this great nation. Arlene Foster
Relations between the Prime Minister and the DUP have continued to deteriorate as Theresa May continually seeks to find agreement on the Withdrawal Agreement. While the Tories and the DUP have a confidence and supply arrangement to allow Theresa May to run her government, it is Labour the Prime Minister has turned to in order to find the support needed for her deal.
On Wednesday evening EU leaders met at an emergency summit to discuss the Mrs May's latest request for a delay to Brexit. It is rumoured she will be offered a long delay with an option to leave earlier should agreement be found.
Arlene Foster continued: "Despite the Prime Minister being warned about the opposition to her Withdrawal Agreement, she has limped along and tried to force people into a cul-de-sac where they have no option but to support her deal.
"That is a weak approach and demeans the strength of this great nation. It is also foolish as it traps the UK and burdens future generations with a bad deal.
"Our great democratic principles have been damaged. It is outrageous that almost three years after people voted to leave the European Union, we are potentially facing another European election in the United Kingdom.
"The uncertainty we face is not the fault of the voters. The Prime Minister should recognise that the decision to leave the EU is not the problem but rather the ham-fisted manner in which the negotiations have taken place.”