Phillip Temple, 66, admitted 27 counts of non-recent sexual assault and two counts of perjury at Woolwich Crown Court on Wednesday.
The majority of the abuse took place between 1971 and 1977 when Mr Temple worked for Lambeth and Wandsworth borough councils.
He was tried in the late 1990s but the jury could not decide on a verdict, sparking a retrial which ended in an acquittal, Woolwich Crown Court heard.
Judge Christopher Hehir said: "I am sorry justice was not done when you came to court in 1998 and 1999. He also called Mr Temple a "a wolf in shepherd's clothing".
A victim told the court: "To have trusted institutions such as the church and the legal system allow lawyers to try and discredit me - to seed doubt of my character into the jury about how trustworthy I was - has stayed with me and led to a deep rooted mistrust of myself.
"The perjury taught me that doing the right thing is not rewarded. That playing by the rules is futile. That being sensitive is weak. That trusting in someone, in anything, will only lead to disappointment or worse.
"It taught me that if you have influence, money and power, you can buy lawyers to protect your interests at the expense of what is right."
"I had none of those things. This taught me that in this world, I was nothing."
