Poland has blocked plans to hold a European day against the death penalty, the EU's Portuguese presidency says.
Lech Kaczynski advocates traditional Catholic values
It says Warsaw rejected the idea at a meeting of ministers in Brussels, arguing that any such event should also condemn abortion and euthanasia.
The EU, where the capital punishment is outlawed, had planned to mark the anti-death penalty day on 10 October.
Poland's conservative government has in the past called for a re-opening of the debate on capital punishment.
The European Commission said a conference scheduled to launch the EU day against the death penalty would still go ahead on 9 October.
But with Poland digging in its heels, delegates may find the debate is livelier than they had expected, the BBC's Alix Kroeger in Brussels says.
"Unfortunately, it was not possible to find a consensus among all the 27 [EU] member states," Portuguese Justice Minister Alberto Costa told reporters after the Brussels meeting of EU justice and interior ministers.
EU officials also confirmed that Warsaw alone objected to the move.
Polish Deputy Justice Minister Andrzej Duda said that the EU "should approach the subject in a broader way and debate the protection of life".
"The death penalty is only one element of the debate; there are more - for example, abortion and euthanasia," he said.
This is the latest in a series of political clashes between Brussels and Warsaw, on everything from homosexuality to environmental protection, our correspondent says.
She says that Poland's junior coalition partner, the ultra-conservative League of Polish Families, wants to bring back the death penalty for paedophiles.
Polish President Lech Kaczynski last year called on EU member states to reintroduce the death penalty.
Poland, along with Ireland and Malta, are the only members where abortion is illegal.
Poland's Roman Catholic clergy and politicians have described the practice of euthanasia in countries such as the Netherlands as a "culture of death".
The latest row comes as Poland prepares for early general elections on 21 October.