Ex-pope Benedict XVI asked for forgiveness Tuesday for clerical child sex abuse committed on his watch, but aides rejected allegations of a cover-up while he was archbishop of Munich.

"I can only express to all the victims of sexual abuse my profound shame, my deep sorrow and my heartfelt request for forgiveness," the 94-year-old said in a letter released in response to a German inquiry last month that examined his handling of paedophile priests in the 1980s.

"I have had great responsibilities in the Catholic Church. All the greater is my pain for the abuses and the errors that occurred in those different places during the time of my mandate."

The former pontiff, who stepped down in 2013, was accused in January of knowingly failing to stop four priests accused of child sex abuse in the 1980s when he was archbishop of Munich.

Benedict, who is in very frail health, asked a team of aides to help him respond to the findings by law firm Westpfahl Spilker Wastl (WSW), which had been commissioned by the archdiocese of Munich and Freising to examine abuse cases between 1945 and 2019.

The aides insisted in a statement published by the Vatican alongside his letter Tuesday that "as an archbishop, Cardinal Ratzinger was not involved in any cover-up of acts of abuse".

The former pope -- whose birth name is Joseph Ratzinger -- was the archbishop of Munich from 1977 to 1982.

In one case, a now notorious paedophile priest named Peter Hullermann was transferred to Munich from Essen in western Germany where he had been accused of abusing an 11-year-old boy.

Benedict's team has already admitted to unintentionally giving incorrect information to the report authors denying his attendance at a meeting about Hullermann in 1980.

But they denied any decision was taken at that meeting about reassigning the priest to pastoral duties, and on Tuesday said the abuse was not discussed.

"In none of the cases analysed by the expert report was Joseph Ratzinger aware of sexual abuse committed or suspicion of sexual abuse committed by priests. The expert report provides no evidence to the contrary," the statement said.

 Fear and trembling

In his letter, Benedict said it had been "deeply hurtful" that the "oversight" over his attendance at the 1980 meeting "was used to cast doubt on my truthfulness, and even to label me a liar".

Benedict, who lives in a former monastery within the Vatican walls, said he was "particularly grateful for the confidence, support and prayer that Pope Francis personally expressed to me".

The Vatican moved last month to defend the former pope, saying he had "fought" sexual abuse -- though Pope Francis has publicly stayed silent.

Before his election as pope, Benedict led the Vatican's doctrinal congregation -- once known as the Holy Office of the Inquisition -- giving him ultimate responsibility to investigate abuse cases.

In the letter, dated February 6, he made a clear reference to his failing health, saying that "quite soon, I shall find myself before the final judge of my life".

"As I look back on my long life, I can have great reason for fear and trembling," he said, but was nonetheless "of good cheer" as the end nears.