Pope Benedict XVI says he was hurt by the row over Bishop Williamson
Pope Benedict XVI has written to senior clergy to acknowledge "mistakes" in the lifting of the excommunication of a bishop who has denied the Holocaust.
The Pope says in the letter that the decision had been badly explained and that the Vatican had not checked the bishop's background thoroughly enough.
But he also laments the "hostility" of those who disagreed with the decision.
The Vatican has asked the British bishop, Richard Williamson, to recant his views, but he has not done so.
In a Swedish television interview last November, Bishop Williamson disputed that six million Jews had died at the hands of the Nazis during World War II, and claimed that none had died in gas chambers.
The bishop said last month that if he had known the full harm his comments would cause, he would not have made them.
But the Vatican immediately rejected the apology and told him to "unequivocally and publicly" withdraw his remarks.
The case led to protests from Holocaust survivors, world Jewish leaders and groups, as well as German Chancellor Angela Merkel.
In a letter addressed to the world's Roman Catholic bishops, which the Vatican has not yet released, Pope Benedict admits that Bishop Williamson's case has been mishandled and warns that the Church risks devouring itself with internal squabbles.
I was saddened by the fact that even Catholics who, after all, might have had a better knowledge of the situation, thought they had to attack me with open hostility
Letter from Pope Benedict XVI
In January, the Pope lifted the excommunication imposed 20 years earlier on Bishop Williamson and three other bishops, unaware of his controversial remarks.
In the letter, which was published on Thursday, the Pope acknowledges that the Vatican must in future pay more attention to the internet as a source of information.
"I have been told that consulting the information available on the internet would have made it possible to perceive the problem early on," he says.
"I have learned the lesson that in the future in the Holy See we will have to pay greater attention to that source of news."
The Pope also acknowledges that the Vatican had failed to explain "clearly and adequately" its actions on Bishop Williamson.
He says the affair unleashed an "avalanche of protests" that had hurt him deeply, particularly as much of it had come from Catholics.
"I was saddened by the fact that even Catholics who, after all, might have had a better knowledge of the situation, thought they had to attack me with open hostility," he says.
"Precisely for this reason I thank all the more our Jewish friends, who quickly helped to clear up the misunderstanding and to restore the atmosphere of friendship and trust."
The Pope's letter comes shortly after confirmation that he will visit Israel in May.
The BBC's David Willey in Rome says the Vatican has attempted to put a positive gloss on this unprecedented mishandling of a papal decision, but the fact remains that the image of the Pope, the leader of the world's 1.1 billion Catholics, has been severely dented.
'Gesture of mercy'
The four bishops whose excommunications were lifted are members of the Society of St Pius X, which was founded by a French archbishop, Marcel Lefebvre, in 1970 as a protest against the reforms of the Second Vatican Council.
'I believe there were no gas chambers' - Richard Williamson in November 2008
The late Archbishop Lefebvre made them bishops in unsanctioned consecrations in Switzerland in 1988, prompting the immediate excommunication of all five by the late Pope John Paul II.
The four bishops have been asked by the Vatican to recognise the authority of the Pope and the Second Vatican Council and talks are planned to seek to resolve the "open questions" in the Church's relationship with the Society of St Pius X.
In his letter, the Pope says the intention behind lifting the excommunications was to end the ongoing schism and bring good people back into the fold.
"The discreet gesture of mercy towards four Bishops ordained validly but not legitimately suddenly appeared as something completely different: as the repudiation of reconciliation between Christians and Jews, and thus as the reversal of what the Council had laid down in this regard to guide the Church's path," he says.
Bishop Williamson returned to the UK last month after he was asked to leave Argentina, where he had been the head of a seminary.
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