Sinn Féin has expressed disappointment after a bid to give the North special EU status following Brexit failed to secure European Parliament support.
The party accused the DUP of voting against the democratic will after it helped defeat the measure.
A bloc of left-wing parliamentarians, of which Sinn Féin is a part, proposed the measure in Strasbourg on Wednesday.
It was rejected by MEPs by 374 votes to 66.
A Sinn Féin statement said: "The outcome of (Wednesday's) vote in the European Parliament in Strasbourg is disappointing. This amendment was not put forward by Sinn Féin.
"It is equally disappointing that both the DUP and Fine Gael MEPs voted against the democratically expressed will of the people of the north and Dail Eireann.
"Sinn Féin is continuing to build support for the case for the north to secure designated special status within the EU."
DUP MEP Diane Dodds said Sinn Féin's Brexit charm offensive has failed miserably.
The republican party's demand for special designated EU status for the North post-Brexit has raised unionist concerns that their real motive was to drive a wedge between the region and the rest of the UK.
The fact that Brexit has now been caught up in a reignited debate about a united Ireland has also polarised the issue.
Sinn Féin added: "We have already ensured that the European Parliament is in agreement that the Good Friday Agreement should be protected in all its parts.
"Moreover, the European Council's negotiation guidelines support the need to protect the Good Friday Agreement and recognise the unique circumstances on the island of Ireland and the need for flexible and imaginative solutions.
"We are engaging with hundreds of political representatives and officials from across Europe in order to gather further support for special status for the north within the EU and will continue to do so."
The amendment to legislation in the European Parliament said the 1998 Good Friday Agreement, which largely ended the violence and subsequent agreements, should be fully upheld in the withdrawal agreement.
It said special EU status would also ensure membership of the customs union, single market and the jurisdiction of the European Court of Justice.
It also called for freedom of movement of goods, people and services on the island of Ireland.
Mrs Dodds said the proposals would have prevented the North, as an integral part of the UK, from harnessing new opportunities which flow from Brexit.