Coming closely after taxes, no consumer price increase angers people as much as the rise in train fares. There is a resignation about increases in petrol prices: the blame lies somewhere in the Middle East; global demand for oil seems insatiable and environmental concerns are a mitigating factor. But the recent sharp rise in rail fares, running in some cases at more than three times the rate of inflation, has stung commuters and long-distance passengers alike. It is all the more resented because it is arbitrary, often underhand and at its steepest on rail services that are among the country's worst - dirty, overcrowded and late. Little wonder, therefore, that passengers on the hapless First Great Western's routes have been staging fare strikes, or that government attempts to lure people from their cars are derided as a sham.

Public perceptions, however, can be misleading. The experience of rail passengers has been cruelly uneven. Since privatisation, rail fares on some lines have remained remarkably stable, while others have shot through the roof. So while those travelling from London to Southend find that many tickets cost the same now as in 1995, those travelling to the West Country have had to pay 145 per cent more for a standard single ticket. The big difference is between regulated and unregulated fares, especially between season tickets and those bought on the day of travel. This is because the Government, in allowing privatised operators to set their own fares, feared alienating a powerful group of voters, and protected season-ticket holders and those buying saver tickets. Indeed, for the first five years of privatisation, yearly rises were capped at 1 per cent below inflation - changing then to 1 per cent above it, still seen as an affordable increase.

As a result, rail companies have relentlessly pushed up the cost of walk-on fares, to raise money upfront in pre-bookings and encourage online purchases that are cheaper to process. And secondly they have started varying prices much like airlines, to fill empty seats in slack periods with cut-price tickets while raising the cost of business travel at peak times to stratospheric levels. This, combined with dozens of different special offers and incentives by train operators, means that there is now a bewildering array of fares. This leads to absurdities. It can be cheaper to buy a season ticket and use it only twice a week than to buy two returns; or to get off halfway through a journey and rebook a separate ticket; or to go beyond the intended station and then travel back again on another train.

What angers passengers is the failure, often deliberate, of ticket offices to offer the cheapest fare and the train companies' attempts to whittle away saver fares by lengthening peak periods or cutting back the seats available. This suspicion of stealth rises, like stealth taxes, is reinforced by the Government's trumpeting of its green credentials while quietly forcing train operators to raise fares as the condition of a new franchise.

What is needed is transparency. There is a real need to prevent monopoly operators offering a lousy service exploiting their passengers. Britain's railways are no longer really privatised; the train companies are. It is a hybrid, a Frankenstein's monster of a business. It needs to be reformed. In the meantime, the Office of Rail Regulation should take on an additional task and look at fair fares - for everyone.