The UK's Brexit minister has accused the EU of "legal purism" ahead of a meeting to discuss the NI Protocol.
Lord Frost made the comment in an article for the Financial Times.
In response, Ireland's foreign minister said: "Lord Frost continues to lay blame for difficulty with Protocol at EU inflexibility. This is simply not the case."
Lord Frost is due to meet European Commission Vice-President Maros Sefcovic in London on Wednesday.
The men are due to assess what progress has been made in technical talks aimed at simplifying the operation of the protocol.
Those talks are covering around 30 issues ranging from VAT on used cars, to pet travel and the movement of food products from GB to NI.
UK officials believe that viable solutions are in sight for perhaps two issues, with partial solutions possible in maybe half a dozen other areas.
But the two sides are still far apart on the majority of issues, particularly the possibility of an agri-food agreement.
In his newspaper article, Lord Frost said the UK had "underestimated the effect of the protocol on goods movements to NI, with some suppliers in GB simply not sending their products because of the time-consuming paperwork required."
A UK government impact assessment published shortly after the protocol was agreed in 2019 did say that businesses could expect additional cost and complexity when moving goods from GB to NI.
Lord Frost said in the past week the UK had sent a "detailed proposal" for a veterinary agreement, based on equivalence, and for an authorised trader scheme to reduce paperwork and checks.
But he said "we have had very little back" from the EU.
He added: "The EU needs a new playbook for dealing with neighbours, one that involves pragmatic solutions between friends, not the imposition of one side's rules on the other and legal purism."
Lord Frost continues to lay blame for difficulty with Protocol at EU inflexibility. This is simply not the case. @MarosSefcovic &EU have consistently proposed new solutions.— Simon Coveney (@simoncoveney) June 6, 2021
Is this about media messaging in UK or really solving problems together? https://t.co/c9vDceqsDi
In response Ireland's Foreign Minister Simon Coveney tweeted: "Lord Frost continues to lay blame for difficulty with Protocol at EU inflexibility. This is simply not the case.
"Maros Sefcovic & EU have consistently proposed new solutions.
"Is this about media messaging in UK or really solving problems together?"
In response to that NI First Minister Arlene Foster, the former leader of the DUP, tweeted that Mr Coveney was "just parroting EU commission briefings" which suggested he was "not so interested" in attempts to find solutions.