The rail watchdog is being urged to launch a probe into claims Southern Rail “deliberately sabotaged” services.
Two unions have called on the Office of Rail and Road to investigate amid accusations the company blamed cancelled trains on staff shortages when drivers and guards were actually able to work.
But Southern Rail blasted the allegations, calling them “fabricated nonsense”.
The embattled company is taking a legal case to the Court of Appeal on Monday in a bid to avert strikes planned for next week and January.
Union leaders claimed that a number of trains from Eastbourne in Sussex were cancelled throughout the day on Saturday, even though drivers were available.
Graham Morris, from drivers' union Aslef, said: "Southern is deliberately sabotaging the service to strengthen its argument in court by suggesting that Aslef is responsible for the cancellations.
"Drivers and other crew were sitting around in Eastbourne available to work."
But a Southern spokesman said: "It is the unjustified industrial action by the union which is causing disruption for passengers.
"We are trying to provide the best possible service under very challenging circumstances. If anyone is sabotaging services it's the union."
Mick Cash, general secretary of the Rail, Maritime and Transport union said: "Southern have moved from a position of just peddling lies to one of deliberate sabotage of services just to give them another excuse to stick the boot into their own staff.
"That is a disgraceful and cynical development that proves that the company could not give two hoots about the travelling public, running a safe and reliable rail service or resolving the current dispute.
"Throughout the past year the Office of Rail and Road, supposedly an independent regulator, have either sat on their hands or sided with Southern Rail.
"It is now time for the ORR to get off their backsides and thoroughly investigate this scandal on Britain's biggest rail franchise."
One rail worker in Eastbourne said: "There is a crew room full of frustrated drivers and guards who are puzzled as to why the company would create this disruption and blame it on us."
Additional reporting from Press Association.
