Former detective constables Sharon Patterson, 49, and Lee Pollard, 47, forged documents, concealed evidence and lied about investigations out of laziness and "cynical disdain" for vulnerable victims, the Old Bailey heard.
Jurors were told Patterson ditched work to get a manicure and have a four-hour long lunch at a Chinese restaurant with her married lover Pollard.
When she forged a document to shut down one investigation, Pollard described her as his ‘deceptive partner in crime’ in flirtatious emails, jurors heard.
The couple, of Colchester, Essex, denied wrongdoing between 2011 and 2014, citing administrative chaos at the child abuse unit in north Essex where they both worked.
In March, Pollard was found guilty of two charges of misconduct in public office and Patterson was convicted of one similar offence.
Judge Nigel Lickley QC jailed Patterson for 18 months and Pollard for two years.
He told them they had shown ‘contempt’ for victims when they chose to shut down investigations rather than put in the work, believing they would never be found out.
He told them: ‘People relied on you to do your job to the standard expected. You abused that position for your own selfish purposes.’
If pressure of work was a factor, they should have sought help rather than act as prosecutors, he said.
Patterson broke down in tears as they were sent down from the dock.
Earlier, prosecutor Alexandra Healy QC said the officers' ‘deliberate and dishonest conduct’ had caused harm to the public of the ‘utmost seriousness'.
She highlighted one complainant, who took years to pluck up the courage to come forward, and had felt it was ‘really important it was dealt with properly’.
Mitigating, Jacqueline Carey told the court Patterson had ‘soldiered on’ in a child abuse unit ‘in crisis’ and ‘crippled by the loss of staff’.
The mother-of-three was now virtually penniless, with career prospects that were ‘limited to say the least’, Ms Carey said.
Craig Rush, for Pollard, said he had not set out to act as ‘judge and jury’ in his misguided attempts to ‘separate the wheat from the chaff’.
Mr Rush said: ‘It was not a failing police department, it was a failed police department.
'In a world where public expenditure is pared to the bone there are consequences, and one of those consequences was that this police department had by 2013 failed.’
The convictions brought to a close a four-year corruption probe into the Essex Police unit which was undertaken by the nearby Norfolk force and the police watchdog.
Some 30 officers, some now retired, were investigated, and 296 Essex child abuse cases looked at, of which 55 were referred to the Independent Office for Police Conduct (IOPC).
Patterson and Pollard were the only ones to face criminal charges, but a third officer was sacked for gross misconduct last year.
The misconduct came to light in 2014 after a victim complained her signature had been forged - and misspelled - on a statement taken by Patterson.
While the defendant was on long-term sick leave, the case was reassigned and resulted in a conviction.
Pollard had destroyed four indecent photographs of a complainant in another case while it was still being investigated, the court heard.
He also failed to investigate an allegation of sexual touching by a teenager - then lied by claiming no further action was to be taken, on CPS advice.
In September 2015, Pollard was dismissed for gross misconduct.
He accessed, copied and then disclosed another officer's computerised application for a job promotion without the individual's permission, and then disclosed it to another officer who was considering applying for the same post.
Following her conviction at the Old Bailey, Patterson was also sacked and both now risk losing their police pensions.
In October last year, Detective Constable Peter Wood, who worked at the same unit, was dismissed for gross misconduct for lying during a child abuse case.