Representatives of Christian Churches have expressed concern over last night's vote in the Dáil which has led to the Dying with Dignity Bill progressing to the committee stage.
In a statement, the Irish Catholic Bishops conference has said assisted suicide is often presented as something that would be rare and exceptional.
However, it said that once assisted suicide is accepted in principle, it becomes very difficult to draw a line.
It also said that many countries, which began by legalising assisted suicide on a very limited basis, have moved on to widen significantly the scope of that legislation.
The Moderator of the Presbyterian Church in Ireland, Dr David Bruce, said that the debate addresses matters of the deepest sensitivity.
"We are deeply disappointed and gravely concerned by last night's vote. This Bill of course raises fundamental questions about the value that is placed on human life in Ireland, something that we firmly believe to be a gift from God.
"At the same time, we welcome the acknowledgement by the government, in its failed amendment to the Bill, that there is no human right to access assisted suicide."
Catholic Bishops said they aim to be a voice for vulnerable people.
The Catholic Bishops Conference has asked people to consider the manner in which assisted suicide and euthanasia undermines the whole ethos of healthcare.
"Doctors and nurses are called to be advocates for life and should never be required to assist in any way in the deliberate ending of life.
"We invite you to join us in prayer for those who, at this time, are coming to terms with a diagnosis of terminal illness, that they may have the blessing of a community of compassion and care."
Seven ministers voted for the bill
The bill passed a legislative hurdle in the Dáil last night and will now proceed to detailed scrutiny.
TDs voted in favour of the Dying with Dignity Bill by 81-71 and it will now continue to the committee stage.
A Government motion to set up a special committee to examine the bill for 12 months was defeated.
The bill was sponsored by Solidarity-PBP TD Gino Kenny.
Cabinet ministers backed the Government motion, but all other TDs in the three coalition parties had a conscience vote.
It has emerged that seven Cabinet ministers, including the Tánaiste and the Minister for Health voted in favour of the bill after the Government motion was defeated.
They are Leo Varadkar, Helen McEntee, Simon Harris, Stephen Donnelly, Eamon Ryan, Catherine Martin and Roderic O'Gorman.
Cabinet ministers were bound to support the motion initially, but when that failed they also had a free vote along with all other Government TDs.
Ten Fine Gael TDs supported the bill at that stage - Jennifer Carroll MacNeill, Ciarán Cannon, Bernard Durkan, Alan Farrell, Brendan Griffin, Simon Harris, Emer Higgins, Helen McEntee, Eoghan Murphy and Leo Varadkar.
Four Fianna Fáil TDs also voted for the bill to proceed - Thomas Byrne, Stephen Donnelly, James Lawless and Paul McAuliffe.
Additional reporting Sandra Hurley