Under current laws abortion is admissible in Poland if pre-natal tests reveal a high probability of irreversible damage to the foetus or its affliction with an incurable and life-endangering ailment.
Explaining its verdict, the court said that human life was of value in every development phase, and should therefore be protected by law.
"All public authorities, especially legislators, have the duty to ensure legal protection of every human life," the court said, pointing out that "there can be no talk of protecting human dignity without creating sufficient foundations for the protection of life."
"(A provision which) legalises eugenic practices in the field of the right to life of an unborn child and makes the right to life of an unborn child dependent on his or her health,... is inconsistent ... with the constitution," said Constitutional Tribunal head Julia Przylebska.
The ruling was warmly welcomed by Poland's anti-abortion circles. "Today Poland is an example for Europe, it's an example for the world," said Kaja Godek from the "Stop Abortion" public initiative.
Borys Budka, head of main opposing party Civic Platform (PO), called the Thursday verdict "inhuman". According to Budka it was passed by a "pseudo" constitutional court by order of Jaroslaw Kaczynski, leader of the Law and Justice (PiS) ruling party.
"Kaczynski has shown that he has lost all inhibitions during the time of the COVID-19 epidemic," the PO leader said.
Left-wing politician Barbara Nowacka said the ruling meant it was "time for major revenge."
A group of female left-wing MPs announced the submission to the Sejm (lower house) of a bill that decriminalise abortion. (PAP)