Kirk Reid, dubbed the Night Stalker, was jailed in June 2009 after being convicted of 27 sex offences and two charges of having indecent images of children.
The football coach stalked women on the A24 and in Balham and Tooting, south-west London, often attacking those who had got off night buses.
The Metropolitan Police have linked Reid to 80 to 100 assaults since 2001.
Yesterday the IPCC called the failure to catch the serial sex offender a "shameful chapter in the history of the MPS".
Eight officers were questioned during the eight-month investigation, which concluded "high-ranking" officers missed chances to snare Reid in 2002 and again in 2004.
A chief superintendent and a detective sergeant have received formal words of advice and the other three, none of whom is named, will face a disciplinary panel.
Reid's attacks on young women began in 2001 and were linked on 12 April, 2002. However, police repeatedly focused on another man.