Leaders of the Catholic Church in Ireland have called on people to lobby politicians with their objections to the proposed new law on abortion.
Up to 5,000 people took part in a pro-life vigil at Knock Shrine in Co Mayo.
The procession took place as part of a national prayer vigil for mothers and the unborn.
The event came after the Catholic hierarchy's strong criticism of Government plans to allow abortion in limited circumstances.
Former Taoiseach John Bruton attended the event and said he hopes that the Fine Gael party does not make a mistake and promote legislation that is fundamentally "not in accordance with its values".
Mr Bruton said any examination of the party's policy would show it to be strongly pro-life.
He said legislation now being considered by the Government would deny the weakest human beings of all the right to live.
His concerns were solely confined to the "mere threat of suicide" to permit a termination of pregnancy, he added.
Mr Bruton said he felt that what was being considered was not viable legislation.
It was not consistent with the Constitution, which he argued gave an equal right to the unborn child and its mother.
At the mass, Chief celebrant Cardinal Seán Brady said life was precious and that it had to be promoted, defended and cared for.
He said the Catholic Church was planning to "mobilise" and make people aware of the very important issues at stake in the debate on abortion.
He repeated a call for voters to lobby their elected representatives to oppose any change to the law.
A blessing of expectant mothers was performed during the service.
Pilgrims attending the vigil expressed their concern about proposed legislation that would allow for termination of pregnancy in limited circumstances.
Many of those who travelled to take part in today's event said they fear any liberalisation of the abortion laws in Ireland could lead to terminations on demand in future.
The homily was given by the recently installed Bishop of Limerick Brendan Leahy.
Bishop Leahy said that Ireland was at a crossroads and it was now possible that an abortion regime would be introduced into the country for the first time.
The event was supported by the Irish Bishops' Conference.
It comes after they said the proposed Protection of Life During Pregnancy Bill represented a dramatic and unacceptable change to Irish law.