More than 1,000 Irish citizens have signed a letter to Taoiseach (Irish Prime Minister) Leo Varadkar calling on him to "defend the rights of Irish citizens" in Northern Ireland.
The letter said it was necessary because of Brexit, the "continuing political crisis in the North and the continuing attacks on the Good Friday Agreement".
Signatories include Adrian Dunbar, Frances Black and James McClean.
This is followed in December last year by a similar appeal to Mr Varadkar.
The letter states: "Political institutions remain in suspension as political unionism continues to reject respect for our Irish identity and language, equality of marriage, and access to justice for legacies.
"As you know, these rights are taken for granted by citizens in other parts of these islands."
Attorney Niall Murphy, one of the organizers, said the letter was signed by a "cross section of Northern Nationalist civil society and citizens across Ireland who reflect many professions: business, arts, sports, culture and society".
The full list of signatories was released on Monday.
Analysis: Social and political consequences are overshadowed
By Mark Devenport, political editor of the BBC News NI
This is one of several public letters expressing concern about how Brexit could affect the rights of the people of Northern Ireland.
In December, more than 200 bourgeois nationalists turned to Taoiseach for their protection.
In February, more than 100 trade unionists and others issued an open letter complaining that they would be made invisible in the debate over rights.
The recent letter from citizen nationalists highlights fears regarding health care, education and the loss of voting rights.
This could be a concern that the argument on cross-border trade has overshadowed the potential social and political consequences of Brexit.
As a result of these concerns, a Belfast-based civil rights group filed a formal complaint with the EU Ombudsman.
In October, the EU Ombudsman expressed his sympathy with the complaint, but rejected it because it was outside its mandate.
Mr Murphy helped draft this letter and the letter sent last year, signed by 200 people.
"Together, we want to express a deep sense of anxiety about the ongoing Brexit negotiations," Murphy said.
"The fear that the division on our island by a constitutional crisis, which tries to provoke no Irishman, is deepened by a border.
"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 the rights enjoyed in Donegal continue to remain in Derry and a return to a new frontier in Ireland will not be acceptable. "