In a recent investigation BBC South East journalists say they bought fake tickets and were able to use them on a number of journeys without difficulty.
While the magnetic strips of the tickets do not work, if shown to rail staff the passengers were allowed to go through the barriers with them.
The tickets are being sold on the ‘dark web’ by an alleged group of fraudsters, according to the BBC investigation.
The group, which has not been named, said in a statement, “The train companies keep stuffing their pockets with public subsidies while treating the operation of rail services as an inconvenience.
“No-one should be ashamed of getting one over companies like Southern Rail.
“We wish one day everyone will be able to use an affordable public service. Until then, we will be providing it.”
Southern Rail, run by Govia Thameslink Railway, provides services from Eastbourne to the rest of Sussex and London.
Detective Inspector Jeremy Banks from British Transport Police’s Cyber Crime Unit, said, “We are aware criminals have been using the dark web in order to exploit rail firms by fraudulently selling tickets.
“We take all reports of criminality seriously and our dedicated Cyber Crime Unit works closely with the rail industry as well as police forces nationally to investigate fraud and bring offenders before the courts.
“Anyone can report crime or suspicious behaviour to BTP by sending a text to 61016 or by calling 0800 40 50 40. Alternatively, you can also pass information anonymously to independent charity Crimestoppers on 0800 555 111.”
A spokesperson for the Rail Delivery Group, representing train companies, said, “Fare dodgers deprive the railway of about £200million every year, money which could otherwise be spent improving services. Being in possession of a forged ticket is a criminal offence and risks a hefty fine or prison sentence.
“Train companies work closely with the British Transport Police to combat and investigate fraud, and operators take a range of measures to make sure that customers are buying and using the correct tickets. Staff carry out regular inspections on trains and at stations.
“Sadly there will always be people who try to get away with not paying or to gain financially. The vast majority of passengers who do pay the correct fare don’t feel they should subsidise those who choose not to.”
There will be a report on the BBC One South East Inside Out programme tonight (Monday October 31) at 7.30pm.