A train company which has added a few minutes onto official journey times denies it is a ploy to cut fines for delays.
Thameslink was fined £2.2m last year for late-running trains
Thameslink, which was fined £2.2m for late-running trains last year, said seasonal timetable changes were common practice.
Between one and four minutes have been added to about a third of its 300 daily services between Bedford and Brighton through key London stations.
A spokesman for the Rail Passengers' Council told The Times newspaper it was "disingenuous to tack five minutes on to the timetable and then claim an improvement."
But Thameslink says it is simply a more realistic timetable which will make things clearer for passengers.
The company has seen passengers increase by about 40% over the past five years from 70,000 to 110,000 a day.
More passengers, more delays
Spokesman Martin Water, said more passengers took longer to board trains, creating delays.
He told BBC London: "If we build a little more time into timetables then we don't have so many problems with punctuality, because trains are able to stop at stations for the requisite amount of time.
"Obviously we hope it will make it more punctual because it benefits us, the passengers, it benefits everyone."
He added: "It is more to do with running a service to create a better situation for the customer within the constraints that we have to operate under."