Fitch says a Brexit "could shift the centre of gravity of the EU"
The ratings agency Fitch is warning it may downgrade some European countries' creditworthiness if the UK votes to leave the EU - with Ireland among the 'most exposed' countries.
It says the medium-term outlook of several nations could be affected if the impact is severe.
Fitch says it does not expect to take any "immediate negative rating actions" on other EU countries if the UK left - but that could change if the economic impact was severe or "significant political risks materialised".
Ireland, Malta, Belgium, the Netherlands, Cyprus and Luxembourg are said to be the most exposed countries, as export of goods and services to the UK are at least 8% of their GDP.
The agency says that "Brexit would create a precedent for countries leaving the EU. It could boost anti-EU or other populist political parties, and make EU leaders more reluctant to implement unpopular policies with long-term economic benefits.
"Negotiating the terms of the UK's exit could exhaust the EU's time and energy and open up new fronts of disagreement. Brexit could shift the centre of gravity of the EU, making it more dominated by the eurozone core, poorer, more protectionist and less economically liberal".
It also adds that "if the UK were to thrive outside of the EU, it might encourage other countries to follow suit", and that a Brexit 'could precipitate' Scotland leaving the UK.
Newstalk's Business Correspondent Vincent Wall says Fitch's comments are logical, and our economy could be severely affected if Britain leaves the EU:
Fitch has previously said that a 'leave' vote would trigger a review of Britain's current AA+ rating.
Ryanair earlier unveiled some of its planes that will carry a 'Remain in EU' message for British voters.
Speaking at the Ryanair event, British Chancellor George Osborne said a vote to leave the European Union on June 23rd would be a "one-way ticket to a poorer Britain".