Roger Saint looked after children, both in a residential home and as a foster father in his own home, for six local authorities despite a conviction for the indecent assault on a 12-year-old boy.
He was also appointed to the Clwyd Fostering and Adoption Panel, which helped to vet would-be carers. Police failed to find his earlier conviction when asked to carry out a search because his date of birth was given incorrectly.
But even when the conviction came to light, at least four councils continued to send boys to him, Chester Crown Court was told yesterday. One council believed that his indecency conviction was not significant.
The North Wales Tribunal, investigating abuse of children in care across North Wales, will now investigate the case.
Mr Justice Laws told Saint: "This is a very serious case indeed. It is wholly obvious that you embarked on a deliberate course of masturbating boys in our care over a period of 13 years."
The court was told that Saint either masturbated the boys or told them to masturbate him. In evidence to the police, boys told how their lives had been changed by what had happened. One said: "I will never forget him. He was supposed to look after me. I just hope no-one else suffers like that."
And another said: "I didn't like what he was doing, but I was a child then and I thought he was just being kind."
Saint was convicted of indecent abuse in June 1972. He had previously worked in children's homes in a number of areas, including Hampshire, Wolverhampton and Wiltshire.
Only six months after that conviction, which should have prevented him from working with children again, he started work at a children's home in Manchester and was then officer in charge of a residential school in Merseyside.
In December 1978, he was approved as an adopted parent by Clwyd social services. Clwyd no longer exists but a spokesman for the successor councils said checks had been made with North Wales Police but nothing had been found.
A police spokesman said: "When Clwyd made the inquiry we were supplied with an incorrect date of birth. The vetting procedure was constructed on the basis that the information was correct. Twenty years later there are now no records of the actual check and we are therefore unable to identify where the failing occurred."
In March 1985, Saint became self employed as a full-time foster carer working from home and two years later was appointed a member of the fostering and adoption panel.
In 1988, Saint's previous conviction came to light when Devon Social Services put in a request for a new check after Saint had approached them about two of their children.
Six social service departments placed children with Saint - North Tyneside, North Yorkshire, Tower Hamlets, Greenwich and Clwyd. In total, 19 children were cared for Saint.
By this time at least four of councils were aware of his conviction. Michael Farmer QC said: "The view of Tower Hamlets that it was an isolated incident and children placed with him had been doing well. North Tyneside were aware and their judgment was that [that] conviction was not significant."