The Protection of Life During Pregnancy Bill passed its first hurdle after a 138 to 24 vote in favour, clearing up decades of confusion over the right of women to have abortions in extreme circumstances.
The bill will now come up for final passage next week.
The debate around the European nation's stringent anti-abortion laws was reignited following the death of 31-year-old Savita Halappanavar, who died from septicaemia following a miscarriage in October last year.
Catholic leaders warned that the proposed new law, which faces potential amendments this week, was a "Trojan horse" designed to permit widespread abortion access in Ireland which, almost uniquely in Europe, officially bans abortion in all circumstances.
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Prime Minister Enda Kenny, however, insisted the country's constitutional ban on abortion would remain unaffected.
Ireland's laws on abortion commit the government to defend the life of the unborn and the mother equally. But it has been muddled since 1992, when the Supreme Court ruled that this ban actually meant that terminations should be legal if doctors deem an abortion essential to safeguard the life of the woman, including from her own suicide threats.
This left Irish hospitals hesitant to provide any abortions except for the most clear-cut emergencies and have led to many pregnant women in medical or psychological crises to seek abortions in neighbouring England, where it has been legal since 1967.
The current Irish government has been under pressure to pass a law on life-saving abortions ever since the European Court of Human Rights ruled in 2011 that Ireland's inaction forced women to face unnecessary medical dangers.
Savita's case proved a catalyst after she died at Galway University Hospital last year, a week after being admitted in severe pain at the start of a miscarriage.