The Byford Report said there was an "unexplained lull" in the Ripper's activities between 1969 and 1975.
The inquiry has been made public after being kept secret for nearly 25 years.
Lorry driver Peter Sutcliffe was jailed for the murders of 13 women and the attempted murders of seven others in northern towns between 1975 and 1980.
Sutcliffe was sentenced to a minimum of 30 years in jail for the brutal attacks on women but the 1982 report raises the possibility he may be responsible for other "assaults".
The inquiry into the West Yorkshire Police investigation into the Ripper's crimes includes details of these attacks but this part of the report, entitled "Description of suspects, photofits and other assaults", remains censored by the Home Office.
Also partly censored is a section about Sutcliffe's "immediate associates".
'Established pattern'
The Byford Report points to a "lull" in Sutcliffe's activities between the time when he first came to the attention of the police in 1969 and the first officially recognised Ripper assault in 1975.
Its author, Sir Lawrence Byford, says: "We feel it is highly improbable that the crimes in respect of which Sutcliffe has been charged and convicted are the only ones attributable to him.
"This feeling is reinforced by examining the details of a number of assaults on women since 1969, which, in some ways, clearly fall into the established pattern of Sutcliffe's overall modus-operandi."
Sir Lawrence added that he was "sure" senior police officers were aware of the possibility that the Ripper was responsible for more attacks.
'Major errors'
The report, released under the Freedom of Information Act, details how detectives made "major errors of judgement" during the five years it took to apprehend Sutcliffe.
In 1982, a summary of the report was published, which suggested the police investigation suffered "information overload" because of the massive public response to the hoax letters and tapes sent by John Humble, who became known as Wearside Jack.
Humble was jailed for eight years in March for attempting to pervert the course of justice. His conviction is believed to have influenced the Home Office's decision to finally publish the Byford Report in full.
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Well, why can't they look into this more then?
