In the latest example of his reversion to Church traditions Pope Benedict XVI has instructed Vatican and diocesan officials to use stricter criteria when assessing candidates for sainthood and beatification.

A document made public in the Vatican today calls on bishops to show ''greater sobriety and rigour'' when accepting requests to begin the first phase of proceedings. Cardinal Jose Saraiva Martins, head of the Vatican Congregation for the Causes of Saints, said "certain aspects" of investigating miracles required for canonisation and beatification had proved "problematic'' over the past two decades.

He said that during the pontificate of John Paul II, prospective saints from countries the Pope was about to visit or which lacked a local saint had sometimes been "fast-tracked". Initial inquiries into a prospective saint's life are normally handled in the diocese where he or she lived, and the resulting dossier of evidence is then sent to the Vatican for consideration.

However under John Paul II the Vatican itself sometimes initiated or encouraged the process behind the scenes. John Paul, who believed the world needed saints as inspiring models of behaviour, created more saints than his predecessors put together.

Cardinal Saraiva Martins said the new rules would "respond better to the new spirit introduced by Benedict XVI'', who continues to preside over canonisation ceremonies but has handed beatifications - the step before sainthood - back to lower level prelates.

Beatification, which confers the title Blessed, requires proof of one miracle attributed to the posthumous intercession of the candidate, usually a medically inexplicable cure. Sainthood requires two such miracles. Critics of John Paul II - including some in the Vatican - said he had run a "saint factory" and in doing so diluted or devalued the concept of sainthood.

Cardinal Saraiva Martins however yesterday Monday rejected the "saint factory'' charge, saying people who used the phrase ''know nothing about saints''.

Last December Benedict XVI said saints must contribute to making the Church's message ''more credible and attractive''. The new instructions encourage "meticulous" medical investigation of miraculous cures, and urge those investigating the life of a prospective saint to act objectively and not gloss over or ignore personal faults or defects or other "contrary findings".

The rules lay down that the holiness of candidates for sainthood must be shown to have been "stable, continuous and widespread among people of faith and present in a significant part of the people of God". When questioning witnesses, Vatican investigators must not ask "leading questions" or "suggest an answer".

Those testifying to the holiness of a candidate should be eyewitnesses who had direct knowledge of the person in question and can provide "specific examples", not second-hand impressions. The rule that five years must pass after a person's death before sainthood procedures can begin is retained. It has however been waived even by Benedict himself in several cases, notably those of John Paul II and Sister Lucia dos Santos, the Carmelite nun who was one of the three Portuguese children who saw the visions of the Virgin Mary at Fatima in Portugal in 1917.

Cardinal Saraiva Martins said there had been "no slowdown" under Pope Benedict, with 577 people either canonised or beatified in his first three years as pontiff.