"Observing these consequences I can truthfully say that I regret having made such remarks, and that if I had known beforehand the full harm and hurt to which they would give rise, especially to the church, but also to survivors and relatives of victims of injustice under the Third Reich, I would not have made them," he said.

This is the second public apology from the British-born Williamson, whose excommunication recently was lifted by the Pope. According to a letter posted on his blog Jan. 30, the bishop apologized to Cardinal Dario Castrillon Hoyos for "having caused to yourself and to the Holy Father so much unnecessary distress and problems." Castrillon heads the Pontifical Commission "Ecclesia Dei," which oversees the reconciliation of ultratraditionalist Catholics with the church.

Williamson left Argentina Feb. 24 after the government told him he must leave or face expulsion. Argentina's Interior Ministry said Feb. 19 that Williamson "has concealed the true motive for his stay in the country" because he said he was an employee of a nongovernmental group when he was serving as rector of the seminary of the Society of St. Pius X in La Reja for the past five years. He was removed as head of the seminary in early February.

The Argentine government also said Williamson's remarks that the Holocaust was exaggerated and that no Jews died in Nazi gas chambers insulted and offended Argentine society and the Jewish community.

An Argentine news station showed Williamson, wearing sunglasses and a baseball cap, shaking his fist at a reporter as he left Buenos Aires.

Upon his arrival in London, Williamson was escorted by police to a waiting car. Although he and police were surrounded by journalists with cameras and microphones, the bishop made no comment.

In January Pope Benedict lifted the excommunication of Williamson and three other traditionalist bishops. They were ordained against papal orders in 1988 by the late French Archbishop Marcel Lefebvre, founder of the Society of St. Pius X.

The Vatican later published a statement saying that Williamson would not be welcomed into full communion with the church unless he disavowed his remarks about the Holocaust and publicly apologized.

In his late-February apology, Williamson said: "On Swedish television I gave only the opinion ... of a non-historian, an opinion formed 20 years ago on the basis of evidence then available and rarely expressed in public since.

"However, the events of recent weeks and the advice of senior members of the Society of St. Pius X have persuaded me of my responsibility for much distress caused. To all souls that took honest scandal from what I said, before God I apologize," he said. "As the Holy Father has said, every act of unjust violence against one man hurts all mankind."