The Government's planning for Brexit has been branded "half-baked" after it emerged that the head of the Civil Service here warned the Northern Ireland Office before Christmas that officials were in the dark about what would happen on the border after March 29.
In a letter David Sterling said: "We still await UK Government planning assumptions on specific impacts at the Northern Ireland border."
He also expressed concern about a possible increase in smuggling in the post-Brexit environment, as businesses might not comply with new legal obligations, "leading to the likelihood of a step change in the scale and significance of smuggling and organised crime".
Mr Sterling added that "in practice we will probably see both of these behaviours arising".
Reacting to Mr Sterling's concerns, Ulster Unionist Brexit spokesman Steve Aiken MLA said: "This is indicative of the entire approach that this Government has taken to all the issues around Brexit.
"This lack of any formal planning, this lack of any form of detail is indicative of a completely half-baked solution.
"There seems to have been no forward planning, no detail about the real implications of how it will potentially affect businesses.
"If the head of the Northern Ireland Civil Service says he's not aware of what's needed and what's required, it's indicative of the whole approach by the UK Government and what it's trying to do."
The UUP has called on the Government to request an extension to Article 50 to allow time for detailed planning for Brexit.
The Civil Service confirmed last night that the letter had been sent to the NIO and other Whitehall departments before Christmas.
It's understood that because of the Christmas holidays, no response has yet been received to Mr Sterling's letter.