More than 1,000 Irish citizens have signed a letter to Taoiseach (Irish Prime Minister) Leo Varadkar appealing to him to "defend the rights of Irish citizens" in Northern Ireland.
The letter said this was necessary due to Brexit, "the ongoing political crisis in the north, and the persistent attacks on the Good Friday Agreement".
Signatories include Adrian Dunbar, Frances Black and James McClean.
The letter, published in the Irish News, states: "The political institutions remain in suspension as political unionism continues to deny respect for our Irish identity and language, marriage equality, access to justice for legacy matters.
"As you know these rights are now taken for granted by citizens in other parts of these islands."
Lawyer Niall Murphy, one of the organisers, said the letter has been signed by a "cross section of northern nationalist civic society and citizens from throughout Ireland reflecting many professions; business, the arts, sporting, cultural and community life".
The full list of signatories was published on Monday.
Analysis: Social and political consequences overshadowed
By Mark Devenport, BBC News NI Political Editor
This is one of a series of public letters expressing concern about how Brexit might impact on the rights of people in Northern Ireland.
In December, more than 200 civic nationalists turned to the taoiseach to ask for his protection.
In February, more than 100 unionists and others published an open letter complaining they were being rendered invisible in the debate over rights .
The latest letter from civic nationalists emphasises fears regarding healthcare, education and the loss of voting rights.
This may reflect a concern that the argument over cross border trade has overshadowed the potential social and political consequences of Brexit.
Those concerns led a Belfast based civil liberties group to lodge a formal complaint with the EU Ombudsman.
In October, the EU Ombudsman expressed sympathy with the complaint, but rejected it as being beyond her mandate.
Mr Murphy was involved in drawing up both this letter and the letter sent last year, which was signed by 200 people.
"We collectively seek to give expression to a deep sense of fear in respect of the current Brexit negotiations," Mr Murphy said.
"The fear that partition in our island will be deepened by a border, due to a constitutional crisis that no Irish person has sought to provoke.
"We urge the taoiseach and the Irish government to stand firm in these negotiations, to stand up for the Good Friday Agreement and a rights based society and to ensure that rights enjoyed in Donegal will continue to be enjoyed in Derry and that a return to a border in Ireland will not be acceptable."