Bill allows for abortions when a mother's life is medically in danger and if a woman is in danger of killing herself

Abortion in very limited circumstances is likely to become legal in Ireland on Thursday with the numbers stacking up in the Irish parliament in favour of the groundbreaking reform.

A backbench revolt by Dáil deputies from the main ruling party Fine Gael is only going to amount to up to five of its Teachta Dálas with the protection of life during pregnancy bill likely to be passed on Thursday morning.

The vote will allow for abortions when a mother's life is medically in danger and, more controversially, if a woman is in danger of killing herself if her pregnancy continues. In the latter case a woman asking for termination on grounds of potential suicide will be examined by three doctors.

The introduction of some legal abortions is also a major act of defiance against the power of the Irish Catholic church, whose influence has waned over the last two decades following a deluge of paedophile priest scandals in which the hierarchy was perceived to be protecting clerical sex abusers.

Among the anti-abortion rebels within Fine Gael is cabinet minister for Europe Lucinda Creighton, who will lose the party whip for defying taoiseach Enda Kenny and his government's push for reform.

But independent leftwing TDs pointed out on Wednesday evening that the legislation still makes abortion a criminal offence and does not cover the estimated 4,000 plus women who travel to Britain for terminations each year. Six of them, including parliamentarians who have received death threats for their pro-choice stance on abortion, will vote against the legislation because it does not go far enough.

In the marathon parliamentary debate on Wednesday, Joan Collins TD said: "Abortion will remain a criminal offence under this bill, with the threat of a 14-year sentence for women and their doctors – including women who use abortion pills. Combined with the new requirement on doctors and hospitals to justify their decisions for terminating a pregnancy, this will put pressure on doctors to delay terminations until there can be no dispute that a woman's life is at risk – by which time it may be too late."

Speaking before the Dáil discussion Enda Kenny said: "There have been very few bills, probably over the last 40 years that have had such extensive discussion and consultation, and debate in the house."

The taoiseach added "I have no objection to extending the time again tonight, if that be necessary. I don't have any difficulty in dealing with it for that period … but I'm going to get rid of it this evening."

While rightwing Catholic groups have attacked the legislation, claiming it will create a slippery slope towards outright abortion in Ireland, the law has also come under fire from other leftwing Dail deputies.

Socialist party TD Joe Higgins said the legislation was "cowardly" and that serious issues such as fatal foetal abnormalities are "completely ignored". His amendments aimed to bring the focus on the "health of the pregnant woman", he said.

Independent TD Catherine Murphy said thebill was the absolute "bare minimum" and that there would be "further tragedies". She also questioned the amount of money used by anti-abortion campaigners, and the source of the money.

The bill will not cover those women whose babies die shortly after birth from fatal foetal abnormalities and those who seek abortions for other reasons such as poverty. These women will continue to be forced to seek terminations at hospitals and clinics in Britain.

Ireland's near total ban on abortion became the focus of international protests last year after the death of Indian dentist Savita Halappanavar in a Galway hospital. Her husband Praveen said they both requested an emergency termination after her body suffered septic shock but were refused an abortion by medical staff on the grounds that they detected a foetal heartbeat.

An international pro-choice organisation, the Centre for Reproductive Rights, based in New York, said on Wednesday evening that while Ireland was taking an important step towards clarifying the legal criteria for abortion, the parliament and government have kept the law extremely narrow in scope.

Lilian Sepulveda, the director of the centre's global legal program, said: "As currently written, Ireland's abortion law will do nothing to help women who seek to end their pregnancies for many other reasons besides a threat to their lives. This includes women who are pregnant due to rape or incest, who are carrying foetuses with severe impairments and who face other serious risks to their health."