The late Pope Benedict XVI's closest aide has revealed years of tension between the German theologian and his successor Pope Francis in an explosive memoir. 

Georg Gaenswein, Benedict's personal secretary who was seen kissing his wooden coffin in St Peter's Square last week, has embarrassed the Vatican with a series of revelations about the private conversations between the two popes.

The German prelate, 66, revealed Benedict said Francis 'doesn't trust me any more' and claimed the pair clashed over mass traditions, and modernising the church.

To add to the ongoing war inside the Vatican, it has emerged that the late cardinal George Pell warned Francis would be a 'disaster' and a 'catastrophe'.

In Gaenswein's book Nothing but the Truth: My life beside Benedict XVI, he said that it had 'pained Benedict's heart' when Francis effectively reversed his predecessor's decision to relax restrictions on the use of the traditional Latin mass.

In 2021, Francis reimposed restrictions on celebrations of Mass which had been relaxed by Benedict in 2007.

Benedict's ruling had allowed for celebrations of the Old Rite in traditional Latin, with priests often saying the Mass while facing east with their back to the people.

But when Francis overturned it, this was a 'decisive turning point' for Benedict, Gaenswein said.

The book also describes Benedict's perplexity at some of Francis's decisions, and the latter's apparent attempts to keep his predecessor in check.

After becoming the first pope in six centuries to resign in 2013, Benedict promised to live 'hidden from the world', but broke that pledge to speak out on several explosive issues.

The last straw appears to have been a book Benedict co-authored on priestly celibacy in 2020 - a PR disaster that Gaenswein said Francis appeared to blame in part on him.

Gaenswein was effectively fired as head of the papal household with immediate effect.

'Stay home from now on. Accompany Benedict, who needs you, and act as a shield,' he said Francis told him.

Gaenswein, who had been propelled into the limelight on Benedict's election, says he was left 'shocked and speechless' by his demotion.

On hearing the news, Benedict said 'it seems Pope Francis doesn't trust me any more, and is making you my guardian'.

The ex-pontiff intervened and tried to get Francis to change his mind, but to no avail, Gaenswein wrote.

The book also includes a previously unpublished letter from Benedict to Francis in 2013.

In the letter, Benedict insists on two aspects for his successor going forward - that it is necessary to fight against the 'concrete and practical denial of the living God' through abortion and euthanasia, and tackling gender ideology, which he defined as 'manipulation'.

The revelations prompted Francis to summon Gaenswein for a private meeting in the Vatican on Monday to smooth over their relationship.

But the day before, during his weekly Angelus Address, Francis made comments that were considered a thinly-veiled attack at the prelate.

He said: 'The great gossiper is the devil, who always goes around recounting bad things about others, because he is the liar who seeks to divide the church, to distance brothers and sisters and not to create community.'

Gaenswein was a constant presence at Benedict's side after being appointed his secretary in 2003, with the German pair united by their traditional views of how the Church should be run. 

Until his death on December 31 at the age of 95, Benedict had remained a figurehead for the conservative wing, which views Pope Francis as too liberal.

During Benedict's final years living in a monastery in the Vatican grounds, Gaenswein was his gatekeeper.

After Benedict's death, Gaenswein led the mourners, greeting visitors to his mentor's lying-in-state and kissing the coffin in front of tens of thousands at St Peter's Square during the funeral led by Pope Francis.

Like Benedict, Gaenswein was born in Bavaria. He describes his young self as 'a bit transgressive', sporting unruly locks and listening to Pink Floyd.

The son of a blacksmith, he was ordained in 1984 and rose through the ranks to become secretary to the then-Cardinal Joseph Ratzinger.

When Ratzinger was elected to the papacy in 2005, the international media was instantly smitten by his dashing blond-haired assistant.

He was nicknamed 'Bel Giorgio' ('Gorgeous George') and gossip magazines gleefully began splashing paparazzi-style photographs of him in his tennis whites.

His close relationship with Benedict sparked jealousy, he said in the memoir.

But the new pope, Francis, appeared not to want him nearby, Gaenswein said, citing the pontiff's refusal to allow him to live in the palace apartment that Benedict had used.

The memoir is not expected to improve relations between the pair, and it was not clear what job Gaenswein will be given now.

Some Vatican commentators have speculated he could be appointed as a Vatican ambassador, or as director of an important shrine.

Meanwhile, revelations are emerging about Cardinal George Pell's concern about what he considered the 'disaster' and 'catastrophe' of the papacy under Francis.

Mr Pell, who was Francis's first finance minister for three years before returning to Australia to face child sex abuse charges, died on Tuesday at a Rome hospital of heart complications after hip surgery. He was 81.

He had been dividing his time between Rome and Sydney after he was exonerated in 2020 of allegations that he abused two choirboys while he was archbishop of Melbourne.

Australia's High Court overturned an earlier court conviction, and he was freed after 404 days in solitary confinement.

Mr Pell clashed repeatedly with the Vatican's Italian bureaucracy during his 2014-17 term as prefect of the Holy See's Secretariat for the Economy, which Francis created to try to get a handle on the Vatican's opaque finances.

In his telegram of condolence, Francis credited him with laying the groundwork for the reforms, which have included imposing international standards for budgeting and accounting on Vatican offices.

But Mr Pell, a staunch conservative, became increasingly disillusioned with the direction of Francis's papacy, including its emphasis on inclusion and canvassing of the laity about the future of the church.

He wrote a remarkable memorandum outlining his concerns, and recommendations for the next pope in a future conclave, which began circulating last spring and was published under a pseudonym, Demos, on Vatican blog Settimo Cielo.

The blogger Sandro Magister on Wednesday confirmed that Mr Pell was the author of the memo, which is an extraordinary indictment of the current pontificate by a one-time close collaborator of Francis.

Mr Pell remained a figurehead for conservatives during his incarceration and after his exoneration.

The memo is divided into two parts - The Vatican Today and The Next Conclave - and lists a series of points covering everything from Francis's 'weakened' preaching of the Gospel to the precariousness of the Holy See's finances and a 'lack of respect for the law' in the city-state, including in a current financial corruption trial that Mr Pell had championed.

'Commentators of every school, if for different reasons... agree that this pontificate is a disaster in many or most respects; a catastrophe,' he wrote.

Also on Wednesday, conservative magazine The Spectator published what it said was a signed article Mr Pell wrote in the days before he died, describing the 'toxic nightmare' of Francis's two-year canvassing of the Catholic laity about issues such as church teaching on sexuality and the role of women.