The EU has taken a “very belligerent approach” to the difficulties caused by the Northern Ireland Protocol post-Brexit, the DUP leader said.
Arlene Foster also said “something had to give”, and the UK had to take action and extend a grace period limiting red tape associated with the movement of goods from Great Britain into Northern Ireland.
The First Minister added she was “not entirely surprised” by the EU’s threat to take legal action over the matter.
Speaking on BBC Radio 4’s Today programme, Mrs Foster said: “They have taken a very belligerent approach to the difficulties the protocol have caused for Northern Ireland.
“It was quite clear to me that there wasn’t going to be a meeting of minds. So the UK Government was going to have to take action, given that the grace period for goods in terms of supermarkets ended at the end of this month.”
Mrs Foster added: “The number of checks that are occurring between Great Britain and Northern Ireland are so disproportionate to the risk to the EU single market that it has become completely out of step with what the protocol was meant to do.”
“The protocol was meant to do two things. It was meant to protect the single market of the European Union, and it was meant to protect the Belfast agreement, and frankly, it is disproportionately doing one and damaging the other.”
The first of the light-touch regulation schemes on goods from the rest of the UK moving to Northern Ireland had been due to expire at the end of March.
Supermarkets would have had to produce export health certificates for all shipments of animal products since Northern Ireland is part of the EU’s single market.
UK Cabinet member Lord David Frost said the UK’s intervention should allow time for constructive discussions with counterparts in Brussels.
Mrs Foster said it appeared to her from the recent talks between the two sides that the European Union’s answer to the severe difficulties in Northern Ireland was “more protocol”.
“They actually said that the difficulties lay with the UK Government because they weren’t carrying out checks in the appropriate way,” she said.
“There was a need, and something had to give, and the UK Government has a duty to protect the UK internal market, in other words, the market between Great Britain and Northern Ireland.”
She reiterated that the protocol needed to be replaced because the extension of grace periods only acted as “sticking plasters” to what she described as “fundamental problems” in terms of trade.
“There is a fundamental misunderstanding with the European Union as to the damage that they are doing,” she added.
Asked whether Prime Minister Boris Johnson still has the desire to see the protocol replaced, Mrs Foster replied that it was “regrettable” that the PM just wanted to “get Brexit done” and it has led to a situation where people in Northern Ireland were dealing with “very real and tangible problems”.
“They can’t even buy a potted plant from England,” she said.
“It stopped because apparently that goes against the SPS rules for the European Union.”