Cardinal Séan Brady has suggested that EU hostility to religion may have prompted some Irish voters to reject the Lisbon Treaty.
He said a succession of anti-family, anti-life and other anti-Christian decisions by Brussels has made it more difficult for committed Christians to maintain their instinctive support for Europe in the Lisbon Referendum.
Speaking in Co Mayo, the Catholic Primate added that it may be important for the EU to review its pragmatic attitude that compromises essential human, moral and social values.
Cardinal Brady made his remarks during a lecture at Killala's Church of Ireland cathedral on the final day of the Humbert Summer School.
He criticised the EU for promoting secularism at the expense of the Christian heritage of the vast majority of its member states.
He also suggested some Europhile and committed Christian voters in Ireland were prompted by that widespread hostility to religion to reject the Lisbon Treaty.
He warned that ignoring this trend had inevitable political and social consequences, not least on levels of support for the European project itself.
He said it may be important for the EU to review its prevailing pragmatism that results in Christians being denied the right to intervene in public debates, or at least having their contribution dismissed as an attempt to protect unjustified privileges, such as the right to employ supporters of the Christian ethos of institutions like schools.
He said the same might be said of controversies over stem cell research, the status of same sex unions, the primacy of the family based on marriage, and the culture of life.
Complaining that Irish media are so secular, Dr Brady also warned that the founding ideals of the EU could not succeed unless public debate in Ireland reconsidered more strongly our traditional moral values.