New amendments to the omnibus Brexit bill call on the government to rule out putting up a hard border in any circumstances.
People Before Profit want it made law that the government could not take any action that would lead to physical infrastructure on the border.
TD Richard Boyd Barrett says everything needs to be done to avoid a hard border.
"We think that the possibility needs to be ruled out and a clear message needs to be sent to both Britain and the European Union that under any circumstances and for any reason a hard border is out of the question," he said.
Deputy Boyd-Barrett also wants it made clear that the government "will not be facilitating such a border".