In a joint statement, Ireland's bishops, archbishops and lone cardinal described the bill, unveiled this week after decades of debate, as "a dramatic and morally unacceptable change to Irish law."
They argued it would be most grievously wrong to give any woman an abortion to assuage her threats to commit suicide, as the bill allows.
Cardinal Sean Brady, leader of Ireland's 4 million Catholics, said in an interview that the bill made the right to life of the fetus subservient to the rights of the woman. "There are two lives involved here," he said.
The intervention of Ireland's dominant church in the abortion debate raises the political temperature at a moment when the 2-year-old government of Prime Minister Enda Kenny is already fraying over the merits of the bill. The government has been under international pressure to clarify the rights of doctors to perform life-saving abortions since October, when a miscarrying Indian woman died from blood poisoning in an Irish hospital after being denied a termination.
The smaller left-wing party in the coalition, Labour, supports the bill but Catholic conservatives in Kenny's own Fine Gael party are vowing to weaken or block it, chiefly over its suicide section. The bill faces weeks of parliamentary debate and likely amendments before reaching a vote expected in July.
If passed, the bill would permit a single doctor to authorize an abortion if the woman's life was in immediate danger from continued pregnancy; two doctors if the pregnancy posed a potentially lethal risk, such as by triggering the return of cancer in remission; and three doctors if the woman was threatening to kill herself.
Kenny, who has previously clashed with Brady and other Catholic leaders over their admitted involvement in child abuse cover-ups, declined to respond. But Deputy Foreign Minister Eamon Gilmore, the Labour leader, said the bishops had no influence on government policy.
"They're entitled to express their point of view. This is a democratic country. But the laws of this country are made by those of us who are elected by the people and are charged with that responsibility," Gilmore said. "And for 21 years now, legislators have failed to legislate for a Supreme Court decision which set down what was lawful and what wasn't lawful in circumstances where a pregnant woman's life is at risk. It is time that that legislation is dealt with."
In 1992, the Supreme Court ruled that an abortion in Ireland should be lawful only if doctors determined one was necessary to preserve the woman's life. Crucially, the judges found that this rule should apply to women making credible threats to kill themselves if denied a termination.
In 2010, the European Court of Human Rights ruled that Ireland's failure to back the Supreme Court judgment with laws and medical regulations meant Irish doctors were left in legal limbo and women were endangered in the process.
The Strasbourg, France-based court found that doctors sometimes told pregnant patients who needed abortions, particularly to keep their cancer in remission, to travel to England for the procedures. The court ordered Ireland to remedy the situation.
But the government still took no action until the death of Savita Halappanavar. She was 17 weeks pregnant when hospitalized in severe pain at the start of a protracted miscarriage.
Doctors refused her requests to terminate the pregnancy, arguing that the fetal heartbeat must stop first. During a three-day delay, a coroner's inquest found, Halappanavar contracted blood poisoning from ruptured uterine membranes and died of massive organ failure after the fetus' own death.
Ireland has the most severe restrictions on abortion in Europe. An 1861 law makes it a crime punishable by life in prison to procure or perform an abortion. The bill would reduce that maximum prison penalty to 14 years. Dozens of women in Irish maternity wards annually do receive abortions, but only for the most clear-cut medical emergencies.
Malta, the only other European Union member to outlaw abortions except for life-saving purposes, sets the maximum prison sentence at three years. And Poland, which outlaws abortion except in cases involving medical emergencies, incest, rape or serious genetic abnormalities, has no such criminal penalties.
The other 24 EU states all offer wider access to abortion, most notably neighboring Britain, the favored destination for Irish abortion-seekers since England legalized the practice in 1967.
More than 4,000 Irish women receive abortions there annually, while an increasing number induce their own miscarriages at home by using drugs ordered from foreign suppliers via the Internet.