Ryan Coleman-Farrow, 30, who worked in the Metropolitan Police's specialist Sapphire sex crimes unit, falsified paperwork, failed to submit forensic evidence and even falsely told some victims their cases had been dropped.
He pleaded guilty at Southwark Crown Court to 13 counts of misconduct in a public office relating to investigations that he worked on between January 2007 and September 2010.
In mitigation the court was told the incidents began after Coleman-Farrow split from his wife and was diagnosed with cancer.
But passing sentence, Judge Alistair McCreath said the former detective constable had failed vulnerable people who had sought justice.
He told Coleman-Farrow: "In all 13 cases you failed to take steps that were appropriate and necessary for a full and proper investigation of each case, whether by failing to take statements or to gather exhibits or to pass material on to other agencies for further investigation or analysis."
He went on: "All of these people had made complaints of sexual abuse and many of them were particularly vulnerable. Thus the complainants did not have their cases taken to court. Perhaps some of them might never have got that far.
"But whether those cases did get to court or not, those who were thought to be victims of sexual abuse simply did not have their cases properly investigated.
"And you covered up your failure to do them justice by lying and creating false records."
Suspicion first fell on Coleman-Farrow two years ago when a sex worker complained that he had failed to investigate her case properly.
Jaime Perlman, 37, contacted the police to complain that she was being stalked by one of her clients.
But she said Coleman-Farrow, who had been assigned to her case, failed to investigate the allegations properly.
Just days later she and fellow sex worker, Riley Lison-Taylor, who had also complained about police conduct, committed suicide in a chemical filled flat in Putney, South West London.
While no findings were made against Coleman-Farrow in that case, it triggered an investigation by the Independent Police Complaint Commission (IPCC), which uncovered a string of discrepancies in other cases he had been working on.
It was found that the officer, who had been with the unit for two and a half years, had falsified entries on the police's Crime Report Information System claiming the Crown Prosecution Service had decided to drop a case, when no such instruction had been given.
He also failed to get witness statements, did not send exhibits for analysis and claimed forensic tests were negative when they had not been carried out.
Prosecutor Mark Heywood, QC, told the court that in "almost all" of the 13 cases involved, no proceedings had resulted.
A spokesman for the IPCC said: "Our investigation did not reveal systemic or serious supervisory failings. Coleman-Farrow admitted - during his criminal interviews with the IPCC - that in some cases he actively lied and misled his supervisors to cover up his shortcomings and that they would have had no reason to question the validity of the evidence he produced.
"He also told his supervisors - and us - that he was being treated for a serious medical condition although no medical evidence was provided to them or us.
"We may never understand the motives for Coleman-Farrow's actions. He was a rogue officer who deceived his colleagues and concocted evidence to cover his tracks."
Rosemary Fernandes, Crown Advocate for special crime at CPS said: "Over a period of nearly three years, Coleman-Farrow failed to interview alleged victims and suspects, failed to secure forensic analysis, failed to secure CCTV evidence and ultimately failed in his duty to investigate serious allegations of rape and sexual assault.
"He also fabricated CPS decisions on such allegations - which were never in fact referred to the CPS. Victims of crime should have confidence that their allegations will be properly considered by the police and, where appropriate, that the evidence will be reviewed by the CPS for potential prosecution. Coleman-Farrow stood in the way of justice being done."