Published Tuesday, 25 December 2012
Cardinal Seán Brady pictured in Armagh (© Pacemaker)
The Catholic Archbishop of Armagh and Primate of All Ireland said there was no more important value than "upholding the right to life in all circumstances."
His message comes as the Irish Government finalises legislation and regulation to allow for a pregnancy to be terminated if the mother's life is in danger.
This will give effect to the X case judgment, which involved a teenager who became pregnant after being raped in 1992.
A High Court banned her from going to England for a termination, despite having suicidal thoughts.
Twenty years ago, the Supreme Court eventually ruled that despite abortion being illegal in the Republic of Ireland, a woman had the right to seek a termination if her life was in danger, but no legislation was ever put in place.
The campaign was put in the spotlight again in October, after the death of Savita Halappanavar who repeatedly asked for an abortion while she was miscarrying at a Galway hospital.
Cardinal Brady said the new legislation would be a defining moment for Ireland.
"Public representatives will be asked to decide whether a caring and compassionate society is defined by providing the best possible care and protection to a woman struggling to cope with an unwanted pregnancy or by the deliberate destruction of another human life," he said.
"I hope that everyone who believes that the right to life is fundamental will make their voice heard in a reasonable, but forthright, way to their representatives, reminding them that the right to life is conferred on human beings not by the powerful ones of this world but by the Creator.
"No government has the right to remove that right from an innocent person."
The Cardinal also used his message to address the current relations between the Irish Government and the Catholic Church, which are at an all-time low in the wake of the clerical sex abuse scandals.
He said he wished to see faith and public life move beyond what he called "the sometimes negative, exaggerated caricatures of the past".
Meanwhile, the Moderator of the Presbyterian Church Rt Rev Dr Roy Patton has urged people to think about those "who feel socially isolated, abandoned, frustrated, disconnected, and discontented" at this time of year.
"Think about families, as the economy continues to bite and people lose their jobs or can't find one," he said in his Christmas Day message.
"For too many, hope seems in short supply. It was no different that first Christmas when Jesus was born. But the story of Christmas is of hope being born into a hopeless world," he added.