Northern Ireland’s Catholic Bishops have urged Assembly members to reject legislative proposals to broaden the grounds for abortion in a debate scheduled for tomorrow.

The prelates' statement focuses on the amendment to Stormont's Justice Bill that would include "fatal foetal abnormality" as a ground for terminations.

The bishops substitute that terminology by referring instead to "unborn children with life-limiting conditions".

They say if the proposed amendment is passed, some children with a terminal diagnosis would lose their right to life and medical care while others with the same diagnosis would continue to receive treatment and care, based on the choice of their mother.

A Sinn Féin spokesman told RTÉ News the party supports tomorrow's moves to grant abortion in such cases and where rape and incest are involved.

The bishops' statement was issued hours before the SDLP leadership was to decide whether to grant its MLAs a free vote on the measures.

The church leaders states that the reform relating to "fatal foetal abnormalities" would radically change the inherent nature of the right to life, making it contingent on the will of another person.

"Both medical professionals and legislators have a duty to acknowledge that an unborn child with a life-limiting condition, including anencephaly, continues in every clinical and moral sense to be alive and worthy of continuing life-supporting intervention and care until natural death."

The first proposal is in the name of two Alliance party MLAs, Stewart Dickson and Trevor Lunn.

Another Alliance MLA, Anna Lo, has added an amendment to allow abortion in cases of sexual crime.

Green Party MLA Steven Agnew and Basil McCrea, leader of the NI21 party, have tabled similar amendments.

Last November the Northern Ireland High Court ruled that local abortion laws were incompatible with British and European human rights laws.

In the North, abortions are limited to women and girls whose life or health is in grave danger. Twenty-three were carried out in 2013-14. The region was exempted from Britain's 1967 Abortion Act.

DUP leader Arlene Foster has promised to retain the near-total ban but has said she will 'carefully consider' the court ruling which involved a pregnancy resulting from rape.

Like her Deputy First Minister, Sinn Féin's Martin McGuinness, she has vowed to prevent the 1967 Act being extended to the region.

But she told The Guardian newspaper last month that the power-sharing Executive will have to carefully consider the landmark judgment.

Ms Foster said: "It is impossible not to be moved by some couples' heartbreaking experiences. Many of the cases are extremely complex, and increasingly so as medical practice advances.

"Along with executive colleagues I will be taking time to consider carefully Mr Justice Horner's judgment…The legal position (here) is often misunderstood, and many don't appreciate it can permit abortion when the woman's physical or mental health is affected."

Meanwhile, the North's Evangelical Alliance has also issued a statement opposing any liberalisation of the current abortion law.

Its spokeswoman Dawn McAvoy says instances of pregnancy involving life-limiting conditions and sexual crime are extremely difficult and sensitive matters but that compassion for those involved leads it to advocate for better care and support for women and their families in these instances rather than abortion.

"Women deserve better than abortion, even and especially, in these hard cases," her statement continues.

"We are concerned because these amendments would change an important principle in the law in Northern Ireland. At the moment abortion decisions here balance the right to life of both the woman and unborn, and are made on the basis of the woman's life and health.

"Abortions are not allowed for the sole purpose of ending the life of an unborn child. These amendments would mean the decision to abort could be made based solely upon the child's medical condition or their circumstances of conception.

"This creates a legal precedent which denies legal protection to a 'subset' of human life. This is a huge legal, medical and ethical shift."