Bishop Richard Williamson is escorted out of Heathrow Airport by police and security officers after arriving in London on a flight from Argentina Wednesday. (Kristy Wigglesworth/Associated Press)

The Vatican and Jewish groups said Friday they were not impressed with an apology by a British bishop who denied the scale of the Holocaust.

Bishop Richard Williamson belongs to the Society of St. Pius X, an ultraconservative religious order that has been estranged from the Roman Catholic Church for decades. In January, Pope Benedict XVI lifted excommunications of Williamson and three other bishops from the order in a bid to heal the rift.

The pontiff's move ignited an international furor because, only days earlier, Williamson had denied the existence of Nazi gas chambers during the Second World War and alleged that no more than 300,000 Jews died in the concentration camps.

The Holy See, which had demanded a full and public recanting of Williamson's views on the Holocaust, said Friday that Williamson's apology was not enough to allow him to serve as a clergyman in the Roman Catholic Church.

Vatican spokesman Rev. Federico Lombardi said Friday that Williamson's statement "does not seem to respect the conditions" the Vatican set out for him Feb. 4, when it decreed Williamson must "absolutely and unequivocally distance himself" from his remarks.

Charlotte Knobloch, head of Germany's Central Council of Jews, said that by failing to clearly retract "his malicious lies, Williamson has shown again that he is a convinced anti-Semite and an incorrigible Holocaust denier."

Elan Steinberg, vice-president of the American Gathering of Holocaust Survivors and their Descendants, said he could not tell if Williamson's apology was genuine.

"If it is, let him reflect over the coming weeks and make a proper act of penance," he said in an email statement.

"For our part, we seek to move ahead and resume the Catholic-Jewish dialogue with renewed vigour and determination."

In his statement, Williamson expressed regret.

"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. "To all souls that took honest scandal from what I said, before God, I apologize."

Ordered out of Argentina

Williamson arrived in Britain on Wednesday after Argentina's government ordered him out for his views on the Holocaust.

He had been living in La Reja, where he was seminary director of the Society of St. Pius X, since 2003.

The Society of St. Pius X has also distanced itself from Williamson's remarks.

With files from the Associated Press