The Polish government has accused the Catholic Church of shameful blackmail in its attempts to stop parliament passing a law to liberalise IVF treatment for couples facing difficulties conceiving.
In a letter to the government on Monday, Poland's Catholic bishops compared IVF to eugenics.
One bishop said politicians who voted in favour should be excommunicated.
The government says such statements amount to "blackmail".
Prime Minister Donald Tusk said politicians were responsible to citizens, not the Church hierarchy.
The BBC reports IVF is widely used in Poland to help couples who are having difficulty conceiving.