Rail operator Govia Thameslink faces being stripped of its franchises unless performance on its services in the South East of England rapidly improves, the BBC understands.
A source said the government could begin the process within weeks.
Passengers on its Thameslink and Great Northern trains have endured more than a month of disruption following the introduction of new timetables in May.
Meanwhile, commuters are to set receive compensation worth a month’s travel.
Govia Thameslink Railway (GTR) – which also runs Southern and the Gatwick Express services – changed the time of every train on its timetable on 20 May.
Passengers were warned of disruption before the changes were brought in, but the implementation of the new timetable saw some services withdrawn and further cancellations without any warning.
Since then, GTR chief executive Charles Horton has resigned and Transport Secretary Chris Grayling has faced calls to stand down – as MPs from across all parties voiced their concern at the disruption caused in their constituencies.
‘Last chance saloon’
Passengers have been venting their anger on social media, while last week a memo leaked by the RMT union revealed that extra security staff were at stations to protect staff from “unhappy customers”.
But there is also frustration within government that while Northern, which encountered similar problems in the North of England, has introduced an interim timetable, Govia Thameslink’s equivalent is still a fortnight away.
“They are now in the last chance saloon,” a government source told the BBC.
Mr Grayling had previously announced there would be compensation for commuters and an inquiry into what went wrong, saying there had been “major failures” by the rail industry.
A spokesman for Govia Thameslink refused to comment on the reports about the possible loss of the franchises, instead choosing to re-release a statement in which it said it was “sorry for the disruption”.
GTR had added it rescheduled every train in its franchise in an attempt to improve rail efficiency but it was a “hugely complicated task” and involved re-training drivers on new routes.
Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways: