Catholic Bishop of Elphin Christopher Jones told a parliamentary hearing in Dublin that terminating a pregnancy was never morally permissible.
The debate on the issue intensified after 31-year-old Halappanavar died from blood poisoning at the Galway University Hospital on October 28 after doctors allegedly refused to perform an abortion stating "this is a Catholic country".
Speaking at the last of three days of hearings on the abortion issue, Jones said other options were available to the government that did not involve legislating for abortion.
"These include the option of appropriate guidelines, which continue to exclude the direct and intentional killing of the unborn, or a referendum to overturn the X case judgement," he added. "We believe both these options should be fully explored by the Oireachtas."
The parliamentary committee is taking evidence ahead of plans to legislate for the X case, in which the Supreme Court allowed for a suicidal pregnant teenager to have an abortion 20 years ago, Irish Times reported.
Bishop Jones, representing Irish bishops, said high standards of maternity care in Ireland are influenced by a mother and unborn child's equal right to life under the constitution.
"This coincides with our belief in the church, based on human reason, and affirmed by sacred scripture, that the life of a mother and her unborn baby are both sacred," he said.
The other religious leaders who gave evidence today included Michael Jackson, Church of Ireland Archbishop of Dublin.
Jackson said his church was opposed to abortion, but recognised there are exceptional cases of undeniable medical necessity were it should be an option.
Heidi Good, of the Methodist Church of Ireland, said abortion on demand was not acceptable but it should be available in circumstances where a mother's life is at risk.
The committee, which will submit a report to Ireland's health ministry by the end of this month to draft legislation, has already heard from senior medics, health chiefs, legal experts and academics.
The Republic of Ireland's stringent anti-abortion laws sparked worldwide protests after Halappanavar's death.
The family of the dentist, who was 17 weeks pregnant, said her death was avoidable as she had asked for an abortion several times before she died.
Ireland's Fine Gael-Labour coalition has said it would bring in legislation and regulation on the issue by the middle of this year.
