A report has suggested the "only winning scenario" for Northern Ireland following Brexit is a united Ireland.
The Costs of Non-Unification - Brexit and the Unification of Ireland report forecasts that both Northern Ireland and the Republic of Ireland will suffer economically after the UK leaves the European Union.
The report examined three potential scenarios: a hard Brexit, in which all of the UK leaves the single market and the customs union, Northern Ireland remaining within the single market and customs union, and the unification of Ireland.
It found that a hard Brexit would reduce Northern Ireland's GDP by 10.1 billion euro (£8.8 billion) from 2021-25.
Northern Ireland remaining within the single market and customs union would result in a GDP dip of 3.8 billion euro (£3.3 billion), it said.
However, the report found that a united Ireland would see Northern Ireland increase its GDP.
"The only winning scenario is the case of unification where between 2018 and 2025, Northern Ireland would increase its GDP by 17.9 billion euro," the report found.
"If political actors nevertheless prefer a hard Brexit, or if they are willing to accept a hard Brexit for overarching political reasons, then they accept willingly high negative economic costs."
The report was produced by Canadian firm KLC Consultants for US-based Irish American organisation KRB Inc.
It comes as negotiations intensify over whether the UK and EU will agree a backstop plan, resulting in Northern Ireland remaining within the customs union after Brexit.
The issue has become a sticking point in the Brexit negotiations.
Read more: Brexplainer - Do you know your single market from your customs union?
Presenting the report at the Europa Hotel on Wednesday, one of the authors, Dr Kurt Hubner, said the Brexit referendum has created enormous change.
"Since the referendum the whole picture has changed enormously, the macro economic situation has changed enormously," he said.
"We already have huge opportunity costs and now with the way we tried to develop those scenarios, it is surprising that the unification one is the only one that would produce positive effects.
"Whereas with a hard Brexit the losses are already piling up."
Sinn Féin vice president Michelle O'Neill and Ulster Unionist Steve Aiken were among those who attended the launch at the Europa Hotel in Belfast today.
Ms O'Neill commended the report as "compelling evidence that could not be ignored".
"This report, and particular economic modelling, exposes the hard economic evidence that reunification would provide a massive economic boost to the entire island," she said.
"In the words of the report, unification 'is the only option with positive net effects'.
"The strength of this evidence cannot be ignored and while we thank Dr Hubner and his team for this valuable contribution, it is a debate that the Irish government must now take a much more proactive role in leading.
"A new generation is already questioning partition, particularly in the context of Brexit, and it is time now for the Irish government to encourage and lead an informed, reasoned and respectful public dialogue on the issue of Irish unity.
"It is also time that the government prepared a realistic plan for Irish reunification, including the establishment of an Oireachtas committee to bring forward a Green Paper for Irish reunification."
Mr Aiken said he was sceptical about the report.
"A figure they say of about 10 billion euro over the space of a decade is absolutely minuscule and is well within the margin for error," he said.
"I can only presume when they continue to put data into the model, they will suddenly realise something we have known all along - that unification is not an answer and would be a net detriment to Northern Ireland."
He added: "And that is very clear because there is no way we can go from one of the largest economies in the world with close on a three trillion GDP into joining something like the Irish Republic that will have significant problems going forward, particularly if the Irish Government continue pushing us towards making sure we have a hard Brexit rather than having an appropriate Brexit for everybody."
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