A rise in peak-time fares for rail passengers would just be a tax on commuters and should not be considered by the Government, a report by MPs has said.
Reducing the cost of the railways to taxpayers must not be achieved by "ramping up fares", the chairman of the House of Commons Transport Committee Louise Ellman said.
Following Sir Roy McNulty's report into rail costs, the Government is looking at a variety of measures, including managing peak-time demand by increasing fares for those travelling at the height of rush-hour.
The committee's report said: "We recommend that the Government rule out forms of demand management which would lead to even higher fares for commuters on peak-time trains."
The MPs said many lower-paid workers had no choice but to travel at peak times.
The report went on: "Higher prices at peak times might make a difference to demand at the margin but would for the most part be a tax on commuters who have no effective choice over how or when they travel."
The report also recommended that the Government should set out long-term policy on annual season ticket fare increases.
The committee's comments come two days after inflation-busting average rises of 4.2% for regulated fares, which include season tickets, took effect for passengers.
Thousands of passengers in the South East now pay more than £5,000 for an annual season ticket.
This year's regulated fare rise would have been even higher had the Government not pulled back from the original plan of a greater increase.
The committee also said it was "very concerned" about the safety implications of proposals to reduce staffing at stations and on trains.
Launching the report today, Mrs Ellman, a Labour MP, said: "The number of rail passengers has increased but train companies' unit costs have not come down."
Bob Crow, general secretary of the RMT transport union, said: "While this report reinforces once again that our railways are nothing more than a multi-billion pound rip-off lining the pockets of a bunch of spivs and speculators, it ducks the real issue and that's the cast-iron case for public ownership."
Manuel Cortes, leader of the TSSA transport union, said: "This is the clearest warning to ministers against going down the route of rationing rail travel by pricing passengers off trains through super peak-fare tickets."