VATICAN CITY (AP) -- The Vatican delegate running the troubled Legion of Christ urged its priests on Wednesday to elect a new leadership worthy of authority, after suffering for years from shame and suspicion following revelations that its founder was a pedophile.

He said the new leaders must infuse the religious order with a new spirit to finish a process of reform he said had only just begun.

Cardinal Velasio De Paolis presided over a Mass opening a month-long meeting of Legion delegates to elect a new leadership and finalize new constitutions that must be submitted to Pope Francis for approval. The meeting is the culmination of a three-year Vatican experiment to try to turn the congregation around after a Holy See investigation uncovered serious problems in the cult-like movement.

The Legion was once held up as a model by the Vatican, which was impressed by the orthodoxy of its priests and its ability to attract seminarians and donations at a time when vocations were on the decline. But in reality, the order’s founder, the Rev. Marcial Maciel, was leading a double life, sexually abusing his seminarians, fathering three children and creating a twisted system of power that kept most Legion priests in the dark and infected the very life of the order.

The Legion scandal represents one of the worst to afflict the Catholic Church in the 20th century, an egregious example of the church’s concern for the institution over victims of sexual abuse. Despite credible reports sent to the Vatican starting in the 1950s that Maciel was a pedophile, drug addict and manipulative liar, it took until 2006 for then-Pope Benedict XVI to bring Maciel to justice. The Mexican prelate died two years later.

Benedict took the Legion over in 2010 and appointed De Paolis to oversee a whole-scale reform, leading up to the assembly that began Wednesday. While the Legion insists great strides have been made -- decision-making is more decentralized, priests have better training and emails are no longer screened -- De Paolis said the reform has only just begun.

"It has been repeatedly stressed that the revision of the constitutions cannot simply be considered a technical effort, but should be accompanied by a process of examination of life, of review and of spiritual renewal for the institute," he told the gathering of a few hundred priests in the chapel of the Legion’s seminary on the outskirts of Rome. "Thus far, we have only completed the process of preparation."

That assessment may troublesome Legion priests, for whom the General Chapter, as the assembly is called, was to have represented the end of a painful and humiliating ordeal. The Legion’s current superior, the Rev. Sylvester Heereman, recently acknowledged that many of his priests are tired of the process and just want it to end and be told what to do.

But after three years, questions still remain as to how the Legion can even exist when its founder was a fraud and its core mission -- that spiritual inspiration that makes religious orders unique -- remains unclear.

In his homily Thursday, De Paolis acknowledged that this core identity has yet to be nailed down and that the delegates attending the meeting and their new superiors must find a "new spirit, a new heart" to figure it out and move forward in service to the church.

"Choose those whom you deem most worthy and suitable for the ministry of authority," De Paolis said. "For this, it is necessary to free your hearts from resentment, jealousy and envy, and to free your memory so as not to feel burdened by memories that blind and cause suffering."

Legion officials have said they hoped the meeting would result in a return to autonomous government, without any more special Vatican oversight. Francis hasn’t signaled what he might do, other than to say De Paolis’ mandate won’t be renewed.

Legion critics, including many of the hundreds of priests, seminarians and consecrated members who have abandoned it in recent years, have said De Paolis’ reforms didn’t get to the crux of the Legion’s problems and left Maciel’s lieutenants still wielding power and influence.