Criminal gangs are selling hacked pay television services at a fraction of their true cost, a BBC investigation has revealed.
Subscribers to satellite or cable TV can pay more than £80 a month to legitimately receive premium packages.
But fraudsters were caught on camera selling set-top boxes which access equivalent packages for £10 per month.
In light of the findings, experts warned hacked satellite and cable TV is increasing and becoming the "new norm".
One of the fraudsters exposed by the BBC London/Inside Out investigation was Gyula Markovits, a Venezuelan satellite dish installer living in south London. He sold hacked boxes that receive every conceivable channel for less than an eighth of the normal monthly price.
While installing a hacked system, Mr Markovits was secretly recorded saying: "Yes, of course it's illegal - you're getting something for free that you should be paying for.
"They never go after the customers anyway, they go after the guy that runs the network.
"You can buy the box and it shows you all the Sky channels for one year - I do it myself. That's a very underground thing, really."
He boasted that he had 150 customers, generating him almost £20,000 a year in illicit income. Mr Markovits subsequently denied all wrongdoing.
Another fraudster, who called himself Ahmed, sold BBC researchers numerous fraudulent packages from satellite TV shop Golsat in Upton Park, east London.
He said of the £150 access to all Sky movies and sport: "This is nothing for what you [are] going to watch, seriously."
Within days of being confronted with the BBC's evidence, Golsat appeared to shut down.
A poster on the door said it had "closed for refurbishment". Ahmed did not respond to a request for a comment.
Under the Copyright Act, those convicted of supplying the equipment could face a 10-year jail sentence and unlimited fine.
Sky, BT and Virgin have all refused to reveal how many cases of hacked TV they encounter a year.
But the BBC heard of dozens of examples of the fraud spread right across the UK, both tip-offs and cases currently going through the courts.
It is a nationwide problem, with Swansea and Cardiff highlighted as hotspots for pubs using cracked boxes to stream Premier League football.
Keith Cottenden, forensic services director at consultants Cy4or, said there were some areas in the UK where those hacking satellite TV outnumber viewers paying for it legitimately.
He said: "Some of the stats don't make good reading for the providers.
"In some areas, there are not as many subscribers as there are others.
"Within the urban areas, it's widespread - most cities have a wide network of people doing this."
During the investigation, the BBC accompanied City of London Police's Intellectual Property Crime Unit raiding an individual in Liverpool suspected of being the ringleader of a gang supplying the boxes to customers around the country.
Documentation was seized and officers continue to investigate.
The BBC heard reports from the police of numerous gangs. Managers at Golsat and Mr Markovits were recorded saying that they were part of a wider gang, implementing, managing, selling and marketing the devices that perpetuated the fraud.
Dr Luke McDonagh, an expert in copyright law at Cardiff University, said: "The problem is there, it's getting more widespread and the big broadcasters are trying to cut down on it by targeting the criminal enterprises that are running these pirated systems.
"But it's very difficult to crack down on the use of cracked decoders by consumers - so many people are doing it, it is becoming the norm.
"If it continues then we may see the broadcasters having to change their model like the music industry has with things like Spotify - it could become that wide-scale."
The Federation Against Copyright Theft (Fact) said the illegal pirating of paid-for television was not a victimless crime.
Fact spokesman Eddy Leviten said: "Is it fair that someone will be able to steal from someone else and that person will not be not paid for their work?
"That impacts not just on that one single person but on their families as well, all those who rely on that income."
One of the individuals exposed has now been referred to trading standards.
A spokesman for Newham council said that as a result of the BBC's investigation the authority had referred Mr Markovits and his business to its trading standards team.
Between them Sky, Virgin and BT have 17.5m legitimate pay-TV customers.
Inside Out is broadcast on BBC One London on Monday, 10 February at 19:30 GMT and nationwide on the iPlayer for seven days thereafter.