Ireland could become the first country in the world to legalise gay marriage by a national vote, with the country going to the polls on Friday (22 May) in a referendum on same-sex marriage.

For years Ireland has been seen as one of Europe's more socially conservative nations. Homosexuality was only decriminalised in 1993 and abortion is still illegal unless the mother's life is at risk.

The campaigns for both the Yes and No votes have been fierce, with both sides trading accusations of foul play. The No campaign has claimed that Yes campaigners defaced their posters. The Yes campaign alleged that the American far right and the Tea Party have helped to fund the No campaign.

Evana Boyle, a mother and lawyer speaking on behalf of one of the leading No campaign groups, Mothers and Fathers Matter, said that the Yes voters are seeking to radically change the Irish constitution and to change the definition of the traditional family.

"This is radically changing our constitution to redefine marriage and the family. The government is trying to say that it's only about two people saying: 'I do', but it is about the family and changing the definition of the family," she said.

"We're suddenly saying, you know, men and women are interchangeable. Mums and Dads are interchangeable. I think that's extremely radical. We all know mothers and fathers are different. We're in favour of diversity. We're not trying to say everybody is the same. We need to recognise difference, but that's not discrimination."

Olivia McEvoy, the chair of the Irish LGBT federation and her partner Joan O'Brien have been campaigning for a Yes vote. She said it is all about equality.

"No generation should have to go door to door to secure equal status as citizens of any country," she said.

Sitting in their house in Dublin, O'Brien said that the referendum has been ''deeply personal'' for the gay couple, who have been together for 16 years. McEvoy said that the fight to marry has been tough.

"To be scrutinised, to have your life scrutinised, to be the constant source of debate, about whether you are worthy enough to be a parent, or worthy enough to get married and the effect of that has been quite visceral for people," she said.

"Ireland is alive with hope and possibility as a result of this referendum campaign. I want to live there, but the power to realise that Ireland is no longer within our grasp, it's now in the hands of the Irish people."

The Catholic church has chosen to take a back seat in the campaign, leaving it to individual priests to deliver sermons to their own congregations on whether to vote yes or no.

This is a stark change from the 1970s and 1980s when the clergy spoke out publicly and strongly against contraception and divorce that were still illegal in Ireland.

Over 20 years ago, legalising gay sex divided a deeply Catholic society. But a quiet revolution since then has so changed Ireland that now all political parties strongly back the reform. Only two of the 166 parliamentary deputies oppose it.

The waning influence of the Catholic church, its reputation damaged by a series of child abuse scandals, and a rapid rise in support for gay rights from young people in Ireland, have helped to turn public opinion, with the latest Ipsos poll suggesting that 58% of voters will vote Yes on Friday.

Polling stations opened at 6.00am and close at 9.00pm on Friday. A result is expected by Saturday (23 May) across Ireland.