Work to introduce Irish language signage at Belfast's new £340 million bus and rail station has been paused due to a threat of legal action.
It is understood the public transport company Translink has been put on notice about a potential court challenge.
It said no further work to introduce the signage would continue until any legal matters were resolved.
"Design work to include the Irish language on physical signage and on ticket vending machines at Belfast Grand Central Station has now stopped pending potential legal action," it said in a statement.
Sinn Féin Infrastructure Minister Liz Kimmins announced last week that she had approved the move.
In the days since, her decision has been called into question by the DUP. They say it should have been brought to the wider Stormont Executive for approval.
Their ministers plan to bring it up at Thursday's meeting of the executive and have written to Ms Kimmins asking for a detailed breakdown of her decision making.
The additional signage is expected to cost in the region of £150,000. Around £120,000 of it will be spent on new signs for things like platforms and other facilities.
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£28,000 is to be spend reconfiguring ticket vending machines to introduce Irish as a language option on a drop-down menu.
Five languages are already on offer: English, Dutch, German, Italian and Spanish.
DUP leader Gavin Robinson claimed this morning that one of them would have to be dropped in order to include Irish.
Translink now says it is looking at a number of options, including adding Irish as a sixth offering.
"The options to include Irish language on ticket vending machines would need to be further explored with the supplier. The options could include adding this to the current language offering or making a substitute," it said.
The new transport hub opened last September amidst a fanfare.
All cross-border bus and rail services now run to and from it.
Irish language activists had demanded that the language be visible in the new facility.
'Genuine concern' over Irish signs, says Little-Pengelly
Earlier, Northern Ireland Deputy First Minister Emma Little-Pengelly said a Stormont minister has a "legal duty" to bring a decision to erect Irish language signs at Belfast's Grand Central Station to the executive.
Ms Little-Pengelly said the move by Ms Kimmins did not "constitute value for money or good decision-making".
Minister for Health Mike Nesbitt said he was concerned about the cost of the replacement signage and said he wanted answers as to why the issue was not sorted during the construction of the transport hub.
Meanwhile, Northern Ireland Secretary Hilary Benn said it was a matter for the relevant minister and the Executive, but added that all languages and cultures should be respected.
The Department for Infrastructure said the decision was taken directly by Ms Kimmins, and not by Translink.
Under Stormont rules, ministerial decisions that are deemed significant or controversial should be considered collectively by the power-sharing coalition, rather than by an individual minister.
However, within the Executive, it is ultimately the responsibility of First Minister Michelle O'Neill and Deputy First Minister Emma Little-Pengelly to jointly decide what issues are significant or controversial and should be subject to a wider vote.
Ms Little-Pengelly told the BBC Good Morning Ulster that her concern was the cost of replacing signs that are "virtually new".
She added: "The minister appears to have announced over the course of the last week that she is going to pull those out and replace those at a cost to the taxpayer of £120,000.
"I think there is genuine concern. This is a legitimate question to ask, why on earth would we be doing this at this time?"
Ms Little-Pengelly continued: "Any controversial or significant issue ought to be brought to the Executive.
"The minister has not done that so we have asked questions about what is the nature of this decision, we will be asking those questions as to why she has not brought that to the Executive.
"The key issue is to get that information and to ask the minister what she is doing.
"If it is an issue which is controversial or significant she has that legal duty under the legislation to bring that matter to the Executive.
"First of all, it is about making that absolutely clear to the minister. The minister then has a decision to make about bringing that. That decision is not rightfully taken, it is not a decision that she can take alone, she would need to bring that to the Executive, that is the stage we are at.
"All controversial and significant matters have to be brought to the Executive for Executive agreement. That is the law. The minister should want to abide by the law."
Ms Little-Pengelly added: "To be putting new signs into a building and then ripping them out a few months later to replace them on a particular agenda to me does not constitute value for money, it doesn't constitute good decision-making."
Ulster Unionist minister Mr Nesbitt said the cost of replacing the signage was an issue for him.
He said: "Could you imagine if I decided I wanted tri-lingual language on every building that delivered healthcare, whether it was hospitals, GP surgeries, social care venues?
"That would cost, I would imagine, tens and tens of millions of pounds while people are stuck on waiting lists for year after year.
"I am looking forward to discussing it with Executive colleagues on Thursday morning."
He added: "One of the first questions I want to ask is why has this issue come to the fore so late in the day?
"Why did a previous minister not sort it out during the construction phase of Grand Central Station?"
Grand Central Station has been billed as the largest integrated transport hub on the island of Ireland, with services including trains between Belfast and Dublin.
When the station opened last year disappointment was expressed by the Irish language community that the signage did not incorporate Irish.
Speaking at Westminster, Mr Benn said: "That is a matter for the minister and the department in discussion with Translink, but look my view is we should celebrate and respect all languages and all traditions in Northern Ireland."
"It's a matter in the end for the Infrastructure department and the Executive to sort out.
"But I repeat, we should respect all the languages and all traditions, because that's the way in which Northern Ireland will continue to progress."
Additional reporting PA
