UK proposals to withdraw from the European Convention on Human Rights would rip up the Good Friday Agreement, Amnesty International has claimed.
Home Secretary Theresa May said the convention prevented the deportation of dangerous foreigners.
But Amnesty International Northern Ireland director Patrick Corrigan said the move threatened the human rights upon which the Northern Ireland peace accord was founded.
He said: "Theresa May's proposal to withdraw from the European Convention on Human Rights would mean ripping up the Good Friday Agreement, on which peace in Northern Ireland has been built.
"The Home Secretary's proposal is not just foolish, it is downright dangerous. To undermine an international peace agreement, on which 18 years of peace has been based, is reckless in the extreme."
The human rights treaty was drafted after the Second World War during which millions of Jews perished.
Mrs May said it could bind the hands of Parliament and added nothing to British prosperity.
"If we want to reform human rights laws in this country, it isn't the EU we should leave, but the ECHR and the jurisdiction of its court."
Mrs May cited the cases of clerics Abu Hamza and Abu Qatada, who were at the centre of protracted legal battles in the UK, and a controversial ruling on prisoner voting.
The European Court of Human Rights ultimately backed the extradition of Abu Hamza and four other terror suspects from the UK to the US.
Using the convention, it blocked the deportation of Abu Qatada to Jordan, saying he cannot be deported while "there remains a real risk that evidence obtained by torture will be used against him".
The Home Secretary dismissed suggestions she was against human rights, insisting the UK could protect human rights in a way that does not jeopardise national security or restrict parliamentarians.
The Human Rights Act 1998 was introduced by Labour to enshrine the rights of the convention in UK law.
Ministers are planning to replace it with a British Bill of Rights, but the move has been hit by delays.
Mr Corrigan said: "The European Convention on Human Rights is a cornerstone of the Good Friday Agreement, and has given confidence to people in Northern Ireland that their rights will be protected equally, whatever their religious or political views.
"Given the history of political discrimination and mistrust in policing in Northern Ireland, binding international human rights obligations have been crucial in building and bolstering public confidence in these key structures post-Troubles."