In a message for Holocaust Memorial Day issued through the Irish bishops' press office, Archbishop Sean Brady of Armagh said: "We need to heed the lessons of the Holocaust and learn for the future."
"We know that these lessons have not been learnt, as the genocide of 1994 in Rwanda shows," the message said. "There, 1 million people were murdered within the space of 100 days."
A number of European countries observed the day in honor of the victims of the Nazi-led Holocaust.
"Tuesday, 27 January, Holocaust Memorial Day, marks the anniversary of the liberation of the Nazi concentration camp of Auschwitz-Birkenau," the Irish primate's message said. "One of the purposes of marking this date is to try and ensure that the horrendous crimes committed during the Holocaust are never repeated anywhere in the world."
The message lamented: "Racism and bigotry continue to raise their ugly heads, much nearer home, albeit on a much smaller scale, and in different contexts and circumstances. A truly democratic and tolerant society, free of the evils of prejudice, racism and other forms of bigotry, acknowledges and respects, at all times, the dignity of all its citizens, regardless of race, religion, gender or social condition."
In London, the Anglican archbishop of Canterbury, Rowan Williams, and the Catholic archbishop of Westminster, Cardinal Cormac Murphy-O'Connor, joined Jewish leaders in warning of the resurgence of anti-Semitism.
Chief Rabbi Jonathan Sacks also signed the statement, which challenges in particular anti-Semitic criticism of Israel, the Times reported.
The leaders acknowledge that criticism of any government is a legitimate part of democratic debate. But they insisted that such criticism should not extend to a denial of Israel's right to exist or serve as justification for attacks on Jews around the world. The Times described the statement as "unprecedented in its strength."