VATICAN CITY (Reuters) - Catholic Ireland's stunning decision to close its embassy to the Vatican is a huge blow to the Holy See's prestige and may be followed by other countries which feel the missions are too expensive, diplomatic sources said on Friday.The closure brought relations between Ireland and the Vatican, once ironclad allies, to an all-time low following the row earlier this year over the Irish Church's handling of sex abuse cases and accusations that the Vatican had encouraged secrecy.Ireland will now be the only major country of ancient Catholic tradition without an embassy to the Vatican."This is really bad for the Vatican because Ireland is the first big Catholic country to do this and because of what Catholicism means in Irish history," said a Vatican diplomatic source who spoke on the condition of anonymity.He said Ireland informed the Vatican shortly before the announcement was made on Thursday night.Dublin's foreign ministry said the embassy was being closed because "it yields no economic return" and that relations would be continued with an ambassador in Dublin.The source said the Vatican was "extremely irritated" by the wording equating diplomatic missions with economic return, particularly as the Vatican sees its diplomatic role as promoting human values.Diplomats said the Irish move might sway others to follow suit to save money because double diplomatic presences in Rome are expensive.It was the latest crack in relations that had been seen as rock solid until a few years ago.DAMNING REPORTIn July, the Vatican took the highly unusual step of recalling its ambassador to Ireland after Prime Minister Enda Kenny accused the Holy See of obstructing investigations into sexual abuse by priests.The Irish parliament passed a motion deploring the Vatican's role in "undermining child protection frameworks" following publication of a damning report on the diocese of Cloyne.The Cloyne report said Irish clerics concealed from the authorities the sexual abuse of children by priests as recently as 2009, after the Vatican disparaged Irish child protection guidelines in a letter to Irish bishops.While Foreign Minister Eamon Gilmore denied the embassy closure was linked to the row over sexual abuse, Rome-based diplomats said they believed it probably played a major role."All things being equal, I really doubt the mission to the Vatican would have been on the list to get the axe without the fallout from the sex abuse scandal," one ambassador to the Vatican said, on condition of anonymity.