Joan Freeman has said a referendum should be held on the topic to allow the Irish people to decide the outcome.
On Wednesday night, TD's voted in favour of the Dying With Dignity Bill which will now go forward to the committee stage.
Former Senator Ms Freeman is concerned the legislation will be rushed through.
"When you talk about a committee, we are leaving it up to one hundred people or fifty people to make a decision for the country of a very important nature.
"This is about life and death and once that comes into play, if it does in Ireland, it throws up so many difficult issues."
Many public figures have spoken out in support of the Bill, including health campaigner Vicky Phelan.
Previously, Ms Phelan, who has received a terminal cancer diagnosis said: "Palliative care does not always work, I have seen a number of people over the last two and a half years who have died in a hospice in palliative care.
"It is fantastic when it works but there are times when it does not. There is a certain amount of suffering that no pain management can get on top of.
"I don't want my children to see me like that, all I am asking for is a choice to make that decision."
