VATICAN CITY: Pope Francis on Tuesday issued the most sweeping revision to Catholic Church law in four decades, toughening regulations for clerics who abuse minors and vulnerable adults, commit fraud or ordain women.

The revision, which has been in the works since 2009, involves all of section six of the Church's Code of Canon Law, a seven-book code of about 1,750 articles. It is the most extensive revision since the current code was approved by Pope John Paul in 1983.

The pope reminded bishops that they were responsible for following the letter of the law and that one aim of the revisions was to "reduce the number of cases in which the imposition of a penalty was left to the discretion of authorities".

The new section, involving about 80 articles concerning crime and punishment, incorporates some changes made to Church law since 1983 by the popes and introduces new categories.

Monsignor Filippo Iannone, head of the Vatican department that oversaw the project, said there had been "a climate of excessive slack in the interpretation of penal law," where mercy was sometimes put before justice.

Sexual abuse of minors was put under a new section titled "Offences Against Human Life, Dignity and Liberty," instead of the previously vague "Crimes Against Special Obligations".

That section was expanded to include new crimes such as "grooming" minors or vulnerable adults for sexual abuse and possessing child pornography.