Northern Ireland census figures released today show Catholics are closing the population gap on Protestants.
The new figures put the Protestant population down nearly five points from a 1991 census to 53.1 per cent, and the Catholic population up almost two points to 43.8 per cent of the total population of 1.7 million.
Those who did not indicate any religious belief were asked on the forms what religion they were brought up in.
The Statistics and Research Agency figures showed other religions at 0.4 per cent and 2.7 per cent of people had no religious community background.
The census also disclosed that the vast majority of people in Northern Ireland were white and born there.
In total, 99.2 per cent classified themselves as white, 0.2 per cent were Chinese, 0.2 per cent were of a mixed ethnic background and 0.1 per cent were Indian. The traveller community was estimated 0.1 per cent.
As the political parties in Northern Ireland pored over the census results, unionists and nationalists clashed this evening over the significance of the religious breakdown shown in the figures.
DUP Assembly member Mr Edwin Poots said: "While the raw percentages may show an increase in the Catholic population, it would be a major mistake to extrapolate the information to prove that we will soon be living in a United Ireland.
"In 20 years we could still have the situation that around 44 per cent of the population will be Catholic, so it is not unreasonable to suggest that we can look forward to a further half century of being part of the United Kingdom."
Sinn Féin national chairman Mr Mitchel McLaughlin said: "I don't know of anyone who was arguing that these census figures would actually provide the evidence that constitutional change was about to happen tomorrow.
"But I think it does provide undeniable evidence that such a process of change is under way and it is incumbent on all of us as political leaders to deal with that now, not to ignore it, not to deny it, not to bury our heads in the sand, but to draw confidence and strength from the figures as they exist."
Mr Dermot Nesbitt of the Ulster Unionist Party said: "This type of sectarian headcount must end. We need mature debate, not knee-jerk number-crunching with a sectarian calculator."
His party colleague, Mr David Burnside MP, said: "I feel that unionists have nothing to fear and should take comfort from these statistics.
"They should be more confident that Northern Ireland's position as part of the United Kingdom is reaffirmed and I would suggest that speculation from other political parties on our future is now at an end."
SDLP North Belfast MLA Alban Maginness said: "It is by no means certain that this growth in the nationalist vote will lead to the United Ireland that the SDLP is committed to seeking.
"It is the SDLP's position, in line with the Good Friday Agreement, that there will be a united Ireland if and when the majority votes for one and voters in the south agree."