DUP leader, Ian Paisley, has claimed the referendum on Irish citizenship planned for June signals the end of the Good Friday Agreement.
Mr Paisley said anyone who had previously argued that the Agreement could not be changed had been proven wrong by the Irish Government's decision to push ahead with the referendum.
He said that holding a referendum to change the definition of an Irish citizen from anyone born on the island to only those born here whose parents have lived on the island for three of the four previous years amounts to a unilateral change to the 1998 agreement.
He said unionists had voted for a new agreement last November but had since repeatedly been told it was written in stone and could not be altered.
The referendum proved that this was not so, he said.