Border Communities Against Brexit says Liz Truss’ approach to amend the Northern Ireland protocol is wrong and will introduce border checks on the island of Ireland.
The Bill is currently being discussed by the British Government.
Spokesperson Damien McGenity said these latest developments will "wreck business" across the border region.
Recent CSO data shows how successfully trade is flowing between the islands, with imports from Northern Ireland to the Republic of Ireland up by €357m compared to 2021.
Trade from South to North has increased by €586m during the same period and Mr McGenity says those promoting the Bill need to be honest about the consequences flowing from it.
"This approach is wrong because the amendments will be overridden," he continued.
"There are those who are seeking to create havoc here by supporting this Bill.
"The UK Government has refused to negotiate, instead it is endeavouring to break International Law.
"These actions are disgraceful and should be called out."
