L'Osservatore Romano, a week after proclaiming Tintin a Catholic hero, said the Bard's plays "teem with open references to the Catholic religion."
The newspaper reopened a debate which has raged ever since an Anglican archdeacon said of Shakespeare a few decades after his death: "He died a Papist."
In a lengthy article which appeared alongside a review of the new Shakespeare film, 'Anonymous', L'Osservatore Romano (The Roman Observer) said the references to purgatory in Hamlet and other plays betrayed distinctly Catholic beliefs and marked Shakespeare out as a crypto-Catholic.
The newly released film, which explores the theory that Shakespeare's plays were in fact written by Edward de Vere, the Earl of Oxford, stars Rhys Ifans as the aristocrat and Vanessa Redgrave and Joely Richardson as the older and younger Queen Elizabeth I.
"Shakespeare or not Shakespeare, this is (or seems to be) the problem," wrote L'Osservatore Romano, which has the backing of the Vatican. "His identity may be open to discussion but not his faith." It quoted Rowan Williams, the Archbishop of Canterbury, who during a discussion at the Hay Festival in May said he thought Shakespeare was "probably" a Catholic.
The broadsheet, the Holy See's paper of record, said England was "violently anti-Catholic" during Shakespeare's lifetime and that Elizabeth was "the proud and ruthless defender" of Protestantism, responsible for "bloody persecutions" of Catholics.
A line in the famous 'To be or not to be' soliloquy, when Hamlet refers to "the oppressor's wrong" and the "insolence of office", was an oblique reference to the banning of Catholicism, the paper argued.
The argument that Shakespeare was a Catholic is based in part on documents found in the rafters of a house in Stratford-upon-Avon in the 18th century which suggested that his father adhered to the old faith, the implication being that young Will was covertly brought up a Catholic.
Some scholars have claimed that Shakespeare used a sort of secret code in his writings, in which he described Catholic characters as "high", "light" and "fair" but referred to Anglican characters as "low" or "dark".
Proponents of the idea also point to a will, from a Catholic household in Lancashire, which included a bequest to a 'William Shakeshaft' – the Elizabethan spelling of names being notoriously changeable.
L'Osservatore Romano may be convinced that Shakespeare was a Catholic, but many scholars are not.
"His father was born before the Reformation, so it's no surprise that he was a Catholic, but there is no evidence that William was a crypto-Catholic," said Professor Stanley Wells, the chairman of the Shakespeare Birthplace Trust in Stratford-upon-Avon.
"William was baptised, married and buried by the Anglican Church. There are references to purgatory in his plays but also many references to Anglican theology as well.
"But the possibility always exists. Shakespeare is notoriously elusive and it's very difficult to pin him down on his opinions, religious or otherwise." Earlier this month the Vatican paper hailed Tintin as a "Catholic hero", criticising a decision in Britain to consign one of his adventures, Tintin in the Congo, to the top shelves of book shops on the grounds that it was racist as "politically correct lunacy".