Thousand of rail passengers face fare rises after train companies said they would cut the number of discounted tickets.
People who buy the popular Network Card would be unable to get reductions on any off-peak journey costing less than £10.
The card, costing £20, is used by thousands of passengers to obtain a one-third discount on weekday fares after 10am.
An off-peak day return ticket from Brighton to Worthing costs £3.60. With a Network Card the fare is £2.40.
Rail operators said they were losing between £5 and £10 million a year because the cards were encouraging people to travel on cheaper tickets.
Passengers' groups condemned the move, saying poorer travellers were being targeted because off-peak fares were not regulated.
Phil Gruber, Sussex spokesman for the pressure group Rail Futures, said: "It is no way to encourage people to use the railways."
Operators said there would be no new restrictions on using the cards at weekends or bank holidays.
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