With brazen contempt for the law, criminals set up a sprawling £1.5 million cannabis factory in a disused police station.
Remnants of the massive drugs farm, made up of more than 1,000 plants, were discovered when officers found the building unlocked.
But they arrived too late to catch the culprits, who had cleared out the lucrative crop just hours before.
Campaigners last night said the discovery was a humiliation for Greater Manchester Police, which closed the Failsworth station and four others three years ago.
Critics accused the force of encouraging professional cannabis gangs by effectively 'decriminalising' the drug through their soft treatment of users.
The shocking discovery came as the Government was confronted with yet more evidence of the dire state of policing:
The cannabis farm was discovered at Failsworth station in Oldham on Wednesday. The entire first floor of the building, including the inspector's office, and loft had been taken over for the plants.
The station was shut following budget cuts six years ago and sold via auction to a private owner. Despite the nearest operational police station being less than a mile away, no one had noticed that the building was being used to grow drugs.
When officers searched the building, they discovered plant root balls, soil, empty pots and hydroponic lighting equipment used to cultivate the class B drug.
They admitted it was 'a bit surreal', adding in an online post: 'Officers found the premises insecure and on entering found the remnants of a huge cannabis production. All first-floor rooms and loft space had been used to grow over 1,000 plants.
'It is believed the grow was 'taxed' in the early hours of this morning, where all the cannabis plants had been removed.'
Residents said criminals smashed and boarded up windows to hide the bright lights needed to cultivate plants. Police said the electricity meter had been bypassed.
But no one who spoke to the Daily Mail yesterday said they had smelled the drug or realised what was going on.
One resident who saw the growers leave the premises said: 'I tried to get a look at the number plate. He turned his headlights full on to blind me then shot off. Then the other guy left and I saw he had a large box in the back seat. I heard police found two camp beds in there so they must have been in there all this time.'
David Green, director of the Civitas think-tank, said: 'Most of these growers know that very little will happen to them if they are detected. The police don't seem to be interested in cannabis.
'Where people are found to be growing huge amounts of cannabis they ought to be prosecuted accordingly, but they are not. There are no consequences. We are effectively seeing legalisation by the back door.
'It is rather ironic that a cannabis farm has been found in a disused police station. I'm sure these offenders couldn't resist and got more than a little satisfaction from that fact.'
Mary Brett, chairman of the Cannabis Skunk Sense campaign group, said police forces were not 'proactive' enough about rooting out those using, growing or dealing cannabis. She added: 'The police aren't interested in cannabis in any shape or form. I understand helicopters are expensive, but why can't police forces find these farms by sending up drones with heat-seeking cameras?
'They should be keeping an eye on these big empty buildings or at least encourage the public to report it when they smell the drug.'
Failsworth police station was one of five stations auctioned off by Greater Manchester Police in 2016. It raised nearly £1million for the force, as well as saving £100,000 a year in running costs.
A £3million cannabis factory was found inside a former bingo hall in Northamptonshire last month.
Others have been found in empty banks, GP surgeries, sports centres and even a nuclear bunker in Wiltshire.
Many are controlled by Vietnamese or Albanian gangs, often using trafficked slaves as their minders and 'gardeners'. Cannabis has been linked to depression, suicidal thoughts and psychosis, which causes hallucinations.
Many fear it acts as a gateway to harder drugs. In May, the head of NHS England, Simon Stevens, said Britain risked making a 'big mistake' by relaxing cannabis laws.
Despite the warnings, some police chiefs are actively calling for the drug to be legalised, while others have urged officers to be even more lenient with offenders. The Police Federation, which represents rank-and-file officers, also said forces were having to 'prioritise resources'.
Earlier this year Greater Manchester Chief Constable Ian Hopkins was widely condemned after admitting that up to half of crimes reported to the force were 'screened out' and dropped within 24 hours.
Compiled by Olalekan Adeleye