has been branded an 'ice-cold, cunning Machiavellian' and a 'liar' by one of his cardinals, a German magazine reports.
The anonymous cardinal made the comments in a bombshell interview with
for its 19-page report on the Catholic Church sexual abuse scandal.
He said: "The pope preaches mercy, but in reality he is an ice-cold, cunning Machiavellian, and, what is worse – he lies."
The cardinal was referring to claims that Francis knew about sexual abuse allegations against US Cardinal Theodore McCarrick long before he admitted he was aware of them or took any action.
A report from a high-ranking cardinal in August claimed the pope knew about McCarrick in 2013 - but still employed him as a consultant in naming new American bishops until his resignation in July this year.
The Pope declined to comment.
The report was the main item in this week's Der Siegel magazine which featured a picture of the pope on the front and was titled Du Sollst Nicht Lügen (Thou Shalt Not Lie).
The report criticised the pope's handling of abuse allegations generally, stating: 'He often speaks at inopportune moments, yet in important moments remains silent.'
On Tuesday in Estonia, Pope Francis acknowledged that the sex abuse scandals rocking the Catholic Church are driving people away - and admitted the church must change its ways if it wants to keep future generations.
Francis referred directly to the crisis convulsing his papacy on the fourth and final day of his Baltic pilgrimage, which coincided with the release of the devastating new report into decades of sex abuse and cover-up in Germany.
Francis told a gathering of young people in largely secular Estonia Tuesday that he knew many young people felt the church has nothing to offer them and simply doesn't understand their problems today.
He acknowledged their complaints and said: 'We ourselves need to be converted; we have to realize that in order to stand by your side we need to change many situations that, in the end, put you off.'
Meanwhile, Germany's Catholic Church is expected today to confess to and apologise for thousands of cases of sexual abuse against children, part of a global scandal heaping pressure on the Vatican.
It will release the latest in a series of reports on sexual crimes and cover-ups spanning decades that has shaken the largest Christian Church, from Europe to the United States, South America and Australia.
In Germany alone, almost 3,700 minors were abused between 1946 and 2014, according to the report prepared by the German Bishops' Conference, details of which were leaked to the media earlier this month.
Justice Minister Katarina Barley said the study was 'shocking and probably just the tip of the iceberg'. She urged the Church to "take responsibility for decades of concealment, cover-ups and denials".
Barley also called on the Roman Catholic Church to work with state prosecutors to bring every known case to justice, and to take steps to prevent more abuse.
The independent commissioner for child sex abuse issues, Johannes-Wilhelm Roerig, recommended state authorities step in to clear up the crimes and ensure victims get access to Church files and compensation.
"The state has a duty of care for all children, including those who are in the care of the Church," he told the Sueddeutsche newspaper.
The German Bishops Conference was due to officially release the research paper, which it commissioned four years ago, at the start of a four-day meeting in the western city of Fulda.
A victims support hotline and a dedicated website with information will be put in place during the meeting.
The conference head, Cardinal Reinhard Marx, said earlier this month that bishops were 'deeply depressed, shaken and ashamed before the reality of sexual abuse of minors within the Catholic Church'.