Keith Boots, 55, was responsible for disposing of seized drugs for West Yorkshire Police in Bradford but instead stole large quantities to supply back on to the streets, Leeds Crown Court heard.
He was found guilty of a range of offences on Friday and is expected to be given a lengthy prison sentence when he is sentenced next week.
Detective Superintendent Simon Bottomley, of West Yorkshire Police’s Professional Standards Department, said: “Keith Boots was a criminal masquerading as a police officer who stole class A drugs from the force which he then intended to resupply to the criminal fraternity.
“The actions of Boots were simply inexcusable. Whilst his hardworking and honest colleagues were doing all they could to take illegal drugs off of the streets he was stealing them back and seeking to redistribute them.”
When colleagues raided Boots’s Bradford home in December 2014 they found cocaine, crack cocaine, heroin, ecstasy and cannabis worth around £700,000, including 11kg of cocaine “jammed” into his washing machine, the jury was told.
Prosecutor Paul Greaney QC told the court in January: “What was found on the ground floor would have kept a 1970s rock star, as well as his band, entertained for weeks.”
Opening the case, Mr Greaney asked the jury: “What do you keep in your washing machine? Keith Boots had over 11 kilogrammes of cocaine worth hundreds of thousands of pounds on the street in his.”
The prosecutor said: “It wouldn’t be an exaggeration to say ‘what a stash!’.”
Boots, who had been a West Yorkshire Police officer since 1990 and an inspector for more than 10 years, stole drugs from the stores he managed at Trafalgar House police station in the centre of Bradford.
Officers smashed their way into his home in Norman Lane, Eccleshill, after a colleague noticed a quantity of cocaine missing from the station store.
Mr Greaney said: “What Keith Boots had been doing is as simple as it is wicked.
“In a gross breach of trust, he had been exploiting weaknesses in the system for the destruction of controlled drugs in order to steal them.”
Mr Greaney said Boots, who had a liver transplant earlier in 2014, had become “nothing more than a criminal”.
Boots was found guilty of a range of offences including conspiracy to steal drugs, conspiracy to supply drugs, conspiracy to pervert the course of justice, theft and possessing drugs with intent to supply.
His son Ashley Boots, 30, of Weatherhouse Terrace, Halifax, was found guilty of conspiracy to supply controlled drugs, conspiracy to steal and conspiracy to pervert the course of justice. He admitted six charges of possessing drugs with intent to supply and one count of possessing ammunition.
A third man, Ian Mitchell, 28, of no fixed address, was found guilty of conspiracy to pervert the course of justice.
Mr Bottomley said Keith Boots was dismissed from West Yorkshire Police following a hearing in March last year.
He said: “There is simply no place in West Yorkshire Police for an individual like Boots. He does not belong in a police uniform.”