London, England (CNN) -- A father and son have been convicted of running a "family business" trafficking girls and women into the UK -- including one of their own relations -- to force them to become sex slaves, British police confirmed Tuesday.
Marius Nejloveanu, 23, and his father Bogdan, 51, both from Romania, were found guilty by a Manchester court in northern England of deceiving at least five women, then aged between 15 and 23 years old, into coming to England and making them work as prostitutes in Manchester, Birmingham and on the continent.
"Each of them was identified as a potential victim either because they were young, could be isolated from their family, were low in intelligence or for some reason easily persuaded to come to the UK," prosecuting lawyer Rachel Smith said during the trial.
"All the women were promised they would be helped to find work in the UK. All arrived in the belief they would be offered a home, support and the chance of lawful employment when they arrived."
Detective Inspector Mike Sanderson from Manchester Police told CNN: "One of the victims in this case, when we actually rescued her... was assessed as having the mental age of 10 years old when the fact is she is a 22 year old woman. They are just very, very vulnerable women. They are very immature. They have no adult skills."
Marius Nejloveanu was found guilty of the most serious offenses, including repeated rapes, beating one of the women with a guitar until it broke and threatening another with a knife if she didn't obey him.
"Most of them were raped by him, some were subjected to the most extreme physical and sexual violence and sexual humiliation," prosecutor Smith said.
Detective Constable Colin Ward, from the Sexual Crime Unit, said in a statement: "It is difficult to find the words to describe the physical and sexual abuse these women have endured.
"Marius in particular spun a web of lies to encourage the women to come to the UK, whether by declaring his love for them of promising a better life.
"Instead they became prisoners forced into prostitution. If they complained in any way they would be beaten and raped by Marius. He is a very dangerous man who sees women as a commodity whose only purpose is to serve him financially and sexually."
One woman, who declined to be identified out of a sense of shame and fear of retribution, recalled how Marius Nejloveanu lured her daughter into the prostitution ring. "She thought he wouldn't harm her, and look where she got," the woman, from a small village in Romania, said.
It was only when Marius and Bogdan Nejloveanu were arrested that she first realized something was wrong.
"All the time she was in England with Marius, she would laugh and say 'Mother, don't worry, everything is all right.' She couldn't tell me more, because he was with her all the time. Finally she admitted he beat her, molested her, to make her work for them."
Sanderson explained how the father and son team generated almost $20,000 each month by making the five young women work for 12 hours a day. Police say the exploitation went on for more than four years.
The court heard how Bogdan Nejloveanu gave his son practical help and advice so that he could set up his own prostitution business.
Marius Nejloveanu's phone calls and letters, intercepted by police and presented as evidence in the trial, showed how he even tried to keep trafficking women and prevent other victims from testifying against him, while he was awaiting trial in Manchester's Strangeways Prison.
In a letter to his cousin, Marius Nejloveanu asked him to take a girl to another relative in Spain because "he could bring her over to England to start her on some work and that would be great."
"Also tell her that I love her and that I want to marry her, because if you tell her I want to marry her, she'll fall for that," Marius Nejloveanu wrote.
In separate letter written to the same girl, Marius Nejloveanu implores her to come to the UK. "I want you to come over so I can see you because you are my only true love and I want to be with you for the rest of my life," he said.
"Don't listen to what people say because people are malevolent and evil and it's because of them that I'm in prison. I love you very much and can't wait to see you."
According to one police recording presented in court, Marius Nejloveanu phoned his mother from prison to ask for help in bribing two of the victims so that they wouldn't appear as witnesses in his case.
"If they don't come to the trial then I can be freed," he told her in a phone call from prison. "Tell them you give them work, tell them you give them 10 million to stay at your place. Yes. By Monday we need to know for sure! Ok Mummy?"
Police told CNN they began investigating the Nejloveanus after a social worker became concerned for the welfare of one of the women working at the Shangri-La massage parlor in October 2008. Brought to England on the promise of cleaning work, that woman testified that Marius and Bogdan Nejloveanu told her she had to pay off a $3,000 travel debt by sleeping with strangers for as little as $15.
"We rescued two young ladies who were being exploited and it took several days to actually get them to tell us about the horrible experiences," Sanderson told CNN. "And what we found was that there were three other girls who were from the same sort of brothels who were basically exploiting them.
"The three girls were arrested, we tried to speak to them but unfortunately they didn't want to speak to us and in this case they ended up getting charged with offenses," Sanderson added.
"At the end of the day it turned out that the three girls were doing what they were doing because of the oppression by Marius and Bogdan."
Juanita Huntington, who acted as a "receptionist" at the brothels admitted five counts of controlling prostitution for gain, according to police. She would give the money the girls earned to Marius and report back to him if any did not do as requested by clients. If this happened they would be beaten.
All three are due to be sentenced on Wednesday, January 26.
--CNN's Dan Rivers contributed to this report.