One 12 year-old who was a target for Azad Miah complained to police three times about his harassment in 2008, almost three years before his arrest. She gave up complaining because nothing was done.
Yesterday Judge Peter Hughes QC said that police needed to learn lessons.
Jailing Miah for 15 years at Carlisle Crown Court, the judge said: "This case reveals the seedier side of life in our town and city centres and what can happen to vulnerable and immature girls.
"There are lessons from this case for all of us. There are lessons for parents to learn whose responsibility it is to protect their children.
"There are lessons for those responsible for safeguarding vulnerable teenagers from deprived backgrounds and without appropriate parental care and guidance.
"There are lessons to be learnt by the police to be ever-vigilant to detect signs of the possible exploitation and abuse of vulnerable people, and to take seriously what they say, however chaotic and difficult their lives may be.
"A sad feature of this case is that there were a number of occasions when witnesses complained to police or community support officers about the defendant pestering them but their complaints were not taken further. As a result, opportunities were missed."
Many of the girls preyed on by Miah, 44, were addicted to drugs or came from troubled backgrounds. Some were known to local care authorities. The court was told that he thought they would easily give in to his persistent offers and would be less likely to be believed than him, who purported to be a respectable local businessman.
The married father of four was found guilty of running a brothel above his former Spice of India shop in Carlisle city centre and paying two teenagers for sexual intercourse.
One had intercourse with him out of desperation for cash when she was 15, while he had a sexual relationship with the other, a heroin addict, when she was aged between 15 and 17. A jury also found him guilty of inciting three other girls, one as young as 12, into prostitution.
Detective Inspector Geoff Huddleston, who led the investigation, acknowledged that some victims contacted police "about concerns over employees at the Spice of India" but the information "was not clear, so the true picture of what was happening was not disclosed".
