Stormont's leaders have asked for an urgent meeting with the Government to seek clarity on post-Brexit trading arrangements in Northern Ireland.
First Minister and DUP leader Arlene Foster told the Assembly while she and Sinn Fein had different views on Brexit, they were united in trying to ensure the best possible outcome for people in the region.
Mrs Foster said she and Deputy First Minister Michelle O'Neill would be raising concerns with the Chancellor of the Duchy of Lancaster Michael Gove.
It comes amid conflicting reports on the Government's interpretation of the Brexit withdrawal deal, and whether it intends to fulfil an EU requirement for certain checks to be carried out on goods moving from Great Britain to Northern Ireland.
"Our priority is to ensure that the needs of Northern Ireland are understood and reflected as we move forward," said Mrs Foster during Assembly Question Time.
"Although political differences exist, the Executive are working together to ensure the best possible outcome for people living here.
"We are working to ensure that our businesses do not face increased costs, especially in terms of movement of goods north-south or east-west.
We are in a unique position here, and we have concerns that the interdependencies between the protocol and the trade negotiations are not fully recognised."
Mrs Foster said it would be wrong to restrict trade within the UK's internal market.
"It is important for us to engage with the Chancellor of the Duchy of Lancaster so that we can find out what he means when he says that there will not be any barriers and then work through all of that," she said.
"We are, of course, aware of what the European Union says about the matter, but we are very interested to hear what the United Kingdom Government have to say on the issue because they are the negotiating power in terms of Northern Ireland.
"Therefore, we need to hear what they propose in relation to the protocol and, indeed, in relation to our free trade agreements."
The First Minister said it was vital that Northern Ireland's voice was heard in the negotiations on the future trading relationship.
"It is crucial that we are involved in the decisions that affect directly the people and businesses of Northern Ireland, and, although political differences exist on the issue of leaving the European Union, we are working together as a whole to ensure the best possible outcome for the people living here," she told MLAs.
"We need to have our voice heard, and the deputy First Minister and I have requested an urgent meeting with the Chancellor of the Duchy of Lancaster so that we can raise our concerns and so that we are heard to make sure that there is not a cost put on our businesses - indeed, costs that could then be transferred to our consumers.
"We want to make sure that we have the answers to that, and that is why that meeting with the Rt Hon Michael Gove MP is important."