British is considering to ensure unique requirements of Northern Ireland law.
A coalition of Northern Ireland politicians and human rights activists on Monday threatened a legal challenge against any British government move to leave the European Union unless the province's peace process is protected.
Northern Ireland on June 23 voted to stay in the EU, with 56 percent voting 'Remain', putting it at odds with the United Kingdom's 52-48 percent result in favour of leaving.
Senior Northern Ireland politicians have warned that a British exit could undermine the province's 1998 Good Friday Agreement peace deal by reinstating a hard border with the Republic of Ireland and by undermining the legal basis for the deal, which contains references to the EU.
The peace deal ended three decades of fighting between Catholic nationalists seeking a united Ireland and Protestant unionists who wanted to keep Northern Ireland British in which over 3,600 died.
The group, which includes members of the province's two largest Irish nationalist parties, said in a statement that it would "apply to the High Court in Belfast for leave to apply for judicial review if the Prime Minister fails to commit to comply with the UK's constitutional and legal obligations in deciding whether and when to trigger Article 50."
The British government has said it is considering when to trigger Article 50 of the Lisbon Treaty, which would start a two-year countdown to exit.
The action aims to ensure "the unique requirements of Northern Ireland constitutional law and statute, in particular the statutory recognition of the Belfast-Good Friday Agreement," are safeguarded, the statement said.
At least seven lawsuits have already been brought in England to force the British government to accept that only parliament has the authority to decide whether Britain should trigger Article 50.
© Thomson Reuters 2016