John Bruton says any exit would also raise several more questions
Former Taoiseach John Bruton says "there is a will to find a solution" to Britain's membership of the European Union.
But Mr Bruton, who was appointed EU ambassador to the United States, says Irish workers in Britain could be directly hit if the UK votes to leave the bloc.
"The fundamental issue is whether there's discrimination or not in the workplace", he told Newstalk Breakfast.
"If you have one worker who happens to come from another country being paid less for the same work - simply because he comes from another European country, or she comes from another European country - that's going to be problematic, other than on a very temporary basis".
"That could affect Irish emigrants to Britain who are working temporarily there, that they might not qualify for the universal credit".
"That would run counter to EU law".
He also says a potential 'Brexit' would raise several new questions for Ireland and Europe as a whole.
"Will Scotland want to stay in the UK in those circumstances? Would we have to have border controls within Ireland? What sort of arrangement would Britain have - would it have an arrangement like Norway?".
"The main casualty would be certainty", he added.
British Prime Minister David Cameron faces a race against time today to get a deal on EU reform in time to call a referendum on Britain's EU membership for June.
He spent the early hours of Friday morning in a series of bilateral meetings trying to bridge divides on four areas of his negotiation.
While the Taoiseach Enda Kenny says their membership of the EU is in "Ireland's interest, Britain's interest and Europe's interest".
Mr Kenny has implored EU leaders to "help David" get a quick, strong deal to sell to a sceptical party and his Cabinet.