Sinn Féin and the Democratic Unionist Party tonight declared they would oppose each other in any referendum about the introduction of the euro in Northern Ireland.
Former Stormont health minister Ms Bairbre de Brun confirmed after a meeting with the Northern Ireland in Europe lobby group that her party would campaign for the adoption of the single currency.
But her Democratic Unionist rival in this June's European Parliament election, Mr Jim Allister, said his party opposed the loss of economic sovereignty.
Ms de Brun, whose party reversed its opposition to the euro at its 2003 conference, said Sinn Féin had campaigned against its introduction because "it involved the loss of control over domestic monetary policy, undermined by the dominance of the European Central Bank (ECB).
"This loss of control is a matter of considerable consequence to the Irish economy," the West Belfast Assembly member said. "If a downturn in the global economy occurs, ECB fiscal policy will be dictated by the larger states regardless of its impact on smaller states such as Ireland."
But she said the operation of two different monetary systems on one island was having a negative effect. It also had the potential to exacerbate economic differences. "The adoption of a single currency throughout the island is a crucial part of the process of economic unification," she said.
"The adoption of the euro in the Six Counties would not involve a loss of democratic control, given that there is currently no control over the Bank of England.
"Indeed, entry of the Six Counties into the eurozone will strengthen our demands for greater Irish participation in the decision-making processes of the ECB.
Meanwhile barrister Mr Allister said: "Our message on the big issues of the new constitution and the euro is clear: we believe in the sovereignty of the nation state and therefore oppose political centralisation and the loss of economic control.
"With the Government's shameful refusal of a referendum on the new constitution, we can make the poll on June 10 our opportunity to reject the framework for a European superstate, which is implicit in the proposed constitution."