Pope John Paul II spoke out against the "scandalous behaviour" of Roman Catholic priests who break the vow of chastity, in remarks recalling the sex scandals that have embroiled the church.
"The scandalous behaviour of a few has undermined the credibility of many," the pontiff told a group of visiting bishops from the Philippines, where more than 30 priests were suspended last month for sexual abuse.
The ailing 83-year-old pope has faced a clamour this year over alleged sexual misconduct by Catholic clergy in several parts of the world, including the United States.
"Sadly, the lifestyle of some clergy has been a countersign to the spirit of the evangelical counsels which should be a part of the spirituality of every priest," the pope lamented.
Preparing to mark his 25th anniversary as leader of the Roman Catholic Church, John Paul II said the priesthood could not be regarded as a job like any other but was a vocation that required spiritual training and doctrinal instruction.
"Celibacy is to be regarded as an integral part of the priests exterior and interior life, and not just as a long-standing ideal," he said.
"Todays clergy must be careful not to adopt the secular view of the priesthood as a 'profession', a 'career' and a means of earning a living.
"Rather, the clergy must see the priesthood as a vocation to selfless, loving service, embracing wholeheartedly the 'esteemed gift of celibacy' and all that this involves."
The Vatican last December formally approved tough new measures to punish priests who commit sexual abuse, which include the outright dismissal from the priesthood of clergy found guilty of abuse.
Last month, 34 priests in the Philippines, a predominantly Catholic southeast Asian nation of 80 million people, were suspended for sexual abuse as part of a sweeping reform of the church in the country.
And Catholic bishops issued a rare public apology in July after two senior bishops were implicated in sex scandals.
Last month, the Archdiocese of Boston agreed to pay 85 million dollars to settle more than 500 sexual abuse lawsuits -- the largest public payout ever made by the US Roman Catholic Church.
The Boston archdiocese, which has some two million Roman Catholics, has been the focus of a sexual abuse scandal that a report by the Massachusetts attorney general said has claimed more than 1,000 child victims in the past 60 years.
The report held the church leadership directly responsible for covering up allegations of abuse against nearly 250 priests.
In August, a confidential Vatican document drafted more than 40 years ago was revealed to set out a policy that demanded total secrecy in cases of sex abuse by priests, although officials said it was out of date.