DUP MP Sammy Wilson has been urged to apologise for the consequences of his pro-Brexit position after he claimed the Port of Larne has been told to prepare to become a border control point.
The East Antrim representative made the claim at Westminster yesterday.
The busy port lies in the heart of Mr Wilson's constituency.
He said land is currently being looked at for lorry parking and construction.
During an exchange with Prime Minister Boris Johnson, the DUP MP produced a letter he said has been received by port authorities.
“The Prime Minister has stated that when we leave the EU at the end of this year Northern Ireland will still remain a full part of the United Kingdom.
"Yet I have in my hand a letter received by the management of the Port of Larne only this week stating that they have to prepare to become a border control post and 14 acres has been looked at for car parking or for lorry parking and for construction."
He asked Mr Johnson to explain what the letter means.
"Can the Prime Minister explain how Northern Ireland can remain a full part of the United Kingdom if people coming from the rest of the UK into Northern Ireland have to pass through a border control post and would he advise the management to tear this letter up as well?"
Mr Johnson insisted there will be no new customs infrastructure.
"I haven't seen the letter he describes but I can tell him absolutely, categorically that there will be no new customs infrastructure, for the very simple reason that under the protocol it is absolutely clear in black and white that Northern Ireland is part of the customs territory of the whole of the United Kingdom and will be joining the whole of the United Kingdom in our new independent trade policy and doing free trade deals around the world,” he said.
SDLP MLA Matthew O'Toole last night said Mr Wilson should apologise, saying he "cheered Brexit" and "voted down a deal which would have avoided the checks he now fulminates about".
“If he is annoyed about Brexit's consequences, he can write a letter to himself complaining about Sammy Wilson facilitating it.
“He owns this and he should apologise for it.”
Responding to Mr Wilson's comments, his party colleague Jeffrey Donaldson suggested the proposal relates to "checks on animal health and on the origins of animal products”.
“It's not actually checks on people and in response the Prime Minister was very clear,” he told the BBC.
When contacted last night a spokesman for the port said it had “no comment” to make.
Meanwhile, Secretary of State Brandon Lewis has said the British government "will be setting out more detailed plans for extensive HMRC support for Northern Ireland businesses" in the summer, as he faced cross-party calls for clarity over Brexit trade arrangements.
The Conservative chair of the NI Affairs Select Committee, Simon Hoare, told the House of Commons that businesses "don't quite know what they are preparing for" in the run-up to the end of the transition period.
Mr Lewis said: "We will set out further details to help businesses prepare for the end of the transition period at the earliest appropriate moment ... further guidance will be published this summer to make sure that people and businesses know what they need to do to prepare for the end of the transition period which will be at the end of December this year."
