Changing my religion Part 1: from church to church: The Republic is not as Catholic a country as it used to be. This is due to immigration and to new attitudes, reports Patsy McGarry, Religious Affairs Correspondent

Religion is thriving in the Republic, with more and more people claiming allegiance to a greater variety of faiths. Yet agnosticism and atheism have never had larger followings. So how can we be growing both more and less devout at the same time?

The first explanation is statistical: between 1991 and the last census in 2002, the population grew by more than 10 per cent, from 3.5 million to 3.9 million. Ninety per cent of the extra people are immigrants. Some have no religion, helping to account for the rises in atheism and agnosticism. The vast majority are religious, however - mostly Catholic, which explains that Church's healthy figures, as the number of Irish-born Catholics fell by 15,000.

But the immigrants also include Orthodox Christians, Muslims, Buddhists and others, which means Ireland's religious mix is changing. For example, even though in 2002 an extra 234,300 people called themselves Catholic than did in 1991, , that Church's membership dropped from 91.6 per cent of the population to 88.4 per cent.

Some of that gap is being filled by people with Eastern faiths, as well as people of more familiar beliefs. Church of Ireland members, Presbyterians, Methodists and other non-Catholic Christians accounted for 4.3 per cent of the population at the last census, compared with 3.5 per cent in 1991. (In Northern Ireland, the number of Protestants slipped from 42.8 per cent of the population to 39.5 per cent; Catholics rose from 38.4 per cent to 40.3 per cent. More people also defined themselves as agnostics or atheists.)

And, anecdotally at least, people feel freer about moving religions. Where once they stuck with the Church into which they were born - or gave up religion altogether - it seems they are now more likely to find out what other faiths have to offer and, if they appeal, switch allegiance. Today and tomorrow we shall report several of their stories.

Why is Protestantism growing in the South? (Of the 43,900 extra non-Catholic Christians in the Republic in 2002, 32,000 were immigrants, leaving 11,900 Irish-born converts.) Canon J. L. B. Deane, former honorary secretary to the Church of Ireland general synod, suggests one factor is that a far higher proportion of children in mixed marriages are being brought up in Protestant denominations.

He points out that the Catholic rule that they had to be brought up Catholic no longer holds sway. Many Catholics, he believes, have also been attracted by the less authoritarian style of other Christian denominations.But if Protestantism is on the rise in the Republic, the rate of its growth in popularity is far outstripped by that of Islam, from 3,900 in 1991 to 19,100 adherents in 2002, or 0.5 per cent of the population, and of Orthodox Christianity, from 400 to 10,400, or 0.3 per cent. And people of no religion now make up 3.6 per cent of the population, or 138,300 people, up from 1.9 per cent.