Pope Benedict has apologised to victims of child sex abuse by Irish clergy, saying he felt "shame and remorse".

In a letter to be read to churchgoers on Sunday, the pontiff said: "You have suffered grievously and I am truly sorry."

He also announced a formal Vatican investigation of Irish dioceses, seminaries and religious orders affected by the scandal.

He added that he was willing to meet victims to acknowledge their suffering personally.

Pope Benedict, facing a spreading scandal of child sexual abuse by priests in the Roman Catholic Church, had said he hoped his letter would "help repentance, healing and renewal".

Ireland's Cardinal Sean Brady continues to resist calls to resign for his handling of historic abuse allegations that saw victims sign confidentiality deals.