The Vatican warns that under no circumstances can a gay lifestyle be approved, but that has not stopped rumours and scandals reaching to the very heart of the institution.

This has not just happened over years and decades, but over centuries, leading to inevitable accusations of hypocrisy.

According to several accounts, which are hard to verify 1,000 years later, Pope John XII from the 10th Century had sex with men and boys and was accused of transforming his palace "into a whorehouse".

The 14th Century Pontiff Boniface VIII, who reigned from 1294 to 1303, was said to have declared to a prospective male lover that two men having sex was "no more a sin than rubbing your hands together".

Historical rumour records that Paul II passed away while having sex with a page boy, and that he was succeeded by Sixtus IV, who appointed his lover, Petro Riario, who happened to be his nephew, a cardinal at the age of 17.

While recent popes have been free of gay scandal on a personal level, the rumours and stories of liaisons among the clergy continue to be a feature of Vatican life and are regularly reported in the Italian press.

Pope Francis asked for forgiveness last year, in an apparent reference to two cases of priests and gay sex revealed during a major meeting of bishops.

In October, a Polish monsignor working in the Vatican's doctrinal office since 2003 held a packed news conference in which he disclosed that he was gay and had been living with another man for years.

The Vatican dismissed Monsignor Krzysztof Charamsa, a theologian, from his job there as well as from teaching assignments in pontifical universities in Rome.

A spokesman said at the time that Charamsa's high-profile coming out, on the eve of a meeting of world bishops at the Vatican, was "grave and irresponsible".

After he was fired, Charamsa gave interviews to Spanish and Italian media in which he criticised the Church's rule on celibacy for the clergy. When he apologised, the Pope also appeared to be referring to a scandal exposed in the Italian media about an order of priests who ran a parish in an affluent neighbourhood in Rome.

Parishioners in the Santa Teresa d'Avila wrote to local Church officials reporting that a priest there had had encounters with "vulnerable adults". Newspapers said these took place in a nearby park often frequented by male prostitutes.

In another case, a north Italian priest was defrocked after allegations emerged that he had been surfing the internet to find gay lovers and had been involved in orgies. Among his alleged bedmates were members of the Vatican's Swiss Guard.

Last year, there was a row over the Vatican's attitude towards gay priests when it was claimed that clergy with "homosexual tendencies" were sent to a religious retreat in the city of Trento to be "cured".

The convent's role in trying to 'cure' priests of homosexuality was revealed by former priest Mario Bonfante, who said he was thrown out of the Church for being gay, even though he claimed that he remained celibate.

In an interview with La Repubblica newspaper, he said of the retreat: "It's a place where they help you to rediscover the straight and narrow. They wanted to 'cure' me but I refused to go."

According to its website, the retreat offered priests "an open and tranquil environment in which they can confront their problems" with psychiatrists and psychologists on hand.

Early in his pontificate, Pope Francis was quizzed by journalists on claims that one of his trusted confidantes, a priest appointed to oversee the reform of the scandal-ridden Vatican Bank, had had a series of homosexual trysts while serving as a Vatican diplomat in Uruguay and Switzerland a decade ago.

The 57-year-old monsignor, who had a 15-year career as a Vatican diplomat, allegedly shocked fellow priests and nuns at the Holy See's embassy in Montevideo by having a homosexual affair with a captain in the Swiss army.

The Pope said he had investigated the allegations but found nothing to back them up.

An article in Vanity Fair magazine in 2013 claimed that there were at least a few gay cardinals, including one whose long-term partner was a well-known minister in a Protestant denomination.

The article referred to a notorious monsignor nicknamed "Jessica", who liked to visit a pontifical university and pass out his business card to 25-year-old novices. (Among the monsignor's reported pick-up lines: "Do you want to see the bed of John XXIII?")

In 2007, Monsignor Tommaso Stenico came across a young man in an internet chat room and asked him to his office in the Vatican, where their conversation - in which Stenico denied that gay sex was a sin, touched the man's leg, and said: "You're so hot."

Embarrassingly, the meeting was secretly filmed and then shown on Italian television. According to Vanity Fair, Stenico tried to persuade Italian newspapers that he'd just been playing along in order "to study how priests are ensnared" into gay sex as part of "a diabolical plan by groups of Satanists".

The most senior churchman to get into trouble was Cardinal Keith O'Brien, the archbishop of St Andrews and Edinburgh.

Cardinal O'Brien was a bitter opponent of gay marriage and denounced homosexuality as a "moral degradation".

O'Brien lost his job when three priests and one ex-priest accused him of "inappropriate contact" and predatory behaviour when he was their bishop.

Some of those who have been defrocked have criticised the Church for its hardline stance.

After he lost his job for being in a gay relationship, Vatican priest Charamsa accused the Church of making the lives of millions of gay Catholics globally "a hell".

He blasted what he called the Vatican's hypocrisy in banning gay priests, even though, he said, the clergy was "full of homosexuals".