Allegations of sexual abuse as well as abuse of authority by certain leaders of a religious group in Barcelona have led to an internal investigation by the Vatican, according to the Catholic News Agency (CNA).

Former missionary "Paulino," 36, recently made accusations that he had been a labour and sex slave of certain members of the Missionary Community of Saint Paul the Apostle, and of Mary Mother of the Church (MCSPA) for years. The information was sent to Pope Francis.

He mentioned the names of three priests who he accused of having abused him. The three have a common history in a controversial formation house called "Casa de Santiago," created decades ago in Barcelona to promote late vocations, the CNA report said.

"I have been a labour slave and sexual slave for a group of depraved people, who were protected by church officials," Paulino said in a letter to the pope.

"In the three years I spent at the mission of Natiokotome in Kenya, I was treated like a beast of burden. There were around 30 people, and on top of the slave work there was sexual slavery. They would tell us that an active sexual life is something that God wants, and that He also wants us to go around naked, because that is the way He made us. Help me, Francis. Soothe my broken soul a little. Don't let other youths endure this hell."

In a statement he made to Elpais.com, Paulino described the MCSPA as "a perfect engineering work of evil" and suggested that the Vatican is dealing with a new Maciel case, in reference to the founder of the Legion of Christ, Marcial Maciel who secured the silence of countless Church officials for decades and managed to carry on with his sexual abuse without anyone stopping him –not even the late Pope John Paul II.

Paulino also accused the Church of allegedly covering up his case.

The Vatican, which recently got hold of the letter, is evaluating the information although Pope Francis had already ordered theologian Josè Manuel Vidal to publish the incident, according to news reports.

Paulino's case is not the first claim against the MCSPA sent to Vatican but is believed to be the most significant as it has reached the hands of the pope. Two other testimonies by a young man and young woman have reportedly gotten lost along the way.

In the late 1970s, various news sources also reported a variety of alleged abuses against minors in parishes in Barcelona. The biggest scandal occurred involving an association called Nous Camins (New Ways).