Ireland’s economy would suffer “very serious consequences” if Britain left the European Union, with its exports to the UK falling by up to €3bn (£2.1bn) a year, according to a Dublin thinktank.

The Economic and Social Research Institute (ESRI) warned that exports, investment and opportunities for migration to the UK would all be under threat, if voters in the UK chose to leave the EU in the forthcoming referendum.

David Cameron has promised voters a referendum on continued membership of the EU by the end of 2017. The ESRI said a vote to leave could result in Ireland losing its tariff-free access to the UK consumer market, which could cause exports to drop by up to 20%, or €3bn. Goods imported from the UK would likely become more expensive.

The impact would be more severe on those sectors of the Irish economy that are particularly dependent on exports to the UK, including agriculture and food and drink, the ESRI said.

However, it added that Ireland was far less dependent on exports to the UK than it once was. In 1974, more than half of Irish exports went to the UK; by 2014 it had fallen to just over 15%.

The thinktank also highlights a series of uncertainties that would arise for Ireland, in the event of a Brexit, including the risk that Irish citizens would lose their right to work, visa-free, in the UK.

“A UK exit from the EU opens up the possibility of restrictions on the free movement of people between Ireland and the UK for the purposes of work,” it said.

Almost 400,000 people born in Ireland are resident in the UK, according to the latest official figures, and almost 230,000 British-born people live in the Republic.

“While many of these people in both jurisdictions will have passports which relate to their current residencies as opposed to their places of birth, many others could find themselves post-Brexit being resident in a country where their right to residency has come into question.”