At about 1.40pm on Thursday afternoon, the Irish prime minister, Brian Cowen, reluctantly made the announcement the country has been waiting months to hear: Ireland's next general election will take place on 11 March. Within seconds Twitter was abuzz with Irish expats' excited chatter. "I'm booking my flight home right now," chirped one youthful tweeter. "Can't wait to go back to vote them [Fianna Fáil] out," chimed another.

It is refreshing to see such enthusiasm for representative democracy – which only makes it doubly sad that few, if any, of these politically engaged emigrants will be legally allowed to vote if they do turn up at an Irish polling station in seven weeks' time.

Under Irish electoral law, unless you are "ordinarily resident" in the country (that is living in Ireland on 1 September in the year before the voting register comes into force) you cannot cast a ballot in elections. To live outside the Republic of Ireland and attempt to vote constitutes electoral fraud and carries a maximum sentence of two years in prison.

The contrast with UK passport holders could not be starker. As the Electoral Commission says on its website: "Yorkshire puddings, pubs, and having a good debate over a decent cup of tea with an old friend are just a few things you may miss while you're overseas. But living abroad doesn't stop you having your say back home."

If you're Irish, it does.

More than 110 countries allow passport holders living abroad to vote. Ireland, with its long history of emigration, is not among of them. Unlike citizens of, say, Ghana, Mexico or the Dominican Republic, Irish people living outside the republic are barred from directly participating in the electoral process. Greece, the only other EU member with a similar policy, is in the process of amending its legislation following a successful appeal by two Greek nationals living in France that the law breached the European convention on human rights.

Emigrant voting rights have been on the political agenda in Ireland before, most recently in the 1990s when proposals were put forward to elect representatives of the diaspora to Ireland's second house, the Seanad. Although these comparatively piecemeal suggestions came to naught, the Irish abroad's clamour for greater involvement in political life back home now seems set to intensify.

After a hiatus during the Celtic Tiger days, emigration is once again a reality for hundreds of thousands of Irish men and women. According to the Central Statistics Office in Dublin, between 2006 and 2010 emigration reached a level not seen since the late 1980s. The Economic and Social Research Institute says that about 1,000 people are leaving Ireland every week, a trend that is expected to continue well into 2012.

Just how many of the Irish people moving to the US, Australia, Canada, the UK and other places around the world realise that they lose their vote when they leave is unclear. That they are being disenfranchised is beyond doubt.

As Noreen Bowden, editor of GlobalIrishVote.com, has pointed out, denying emigrants their right to vote has long suited Irish political elites: "Ireland's refusal to allow emigrants voting rights is a tremendous advantage for the insiders of the political establishment, ensuring that a big proportion of those most affected by the economic downturn won't be around to cast their verdict."

However, many in Ireland remain opposed to any extension of the franchise to include emigrants. A popular argument for maintaining the electoral status quo is that with 70 million people of Irish descent living across the globe, the numbers of overseas voters would dwarf the Irish electorate.

As ever, the reality is at odds with the rhetoric. That 70 million figure represents the Irish diaspora in its broadest sense, not Irish passport holders living abroad. According to the Irish department of foreign affairs, there are about 3 million in the latter category.

For a population of less than 4.5 million, 3 million is still a significant number. But based on the figures for expatriate voting from the UK (where you retain your voting rights for 15 years after you leave) and elsewhere, only a small proportion of Irish passport holders abroad would be expected to actually vote – if they were allowed to make that choice.

Instead, as Ireland gears itself up for arguably the most important election since the foundation of the state, the voices of countless Irish emigrants will not be heard.

Ireland deserves change. Allowing those who have left, many forced out by the current government's disastrous economic mismanagement, a fair say in the country's future would be a step in the right direction.