Rail passengers talk about their journeys and the cost of tickets
Rail passengers face fare rises in the new year, with some tickets in England, Scotland and Wales going up by double the rate of inflation.
Regulated and unregulated fares are to increase by averages of 6% and 7% respectively from 2 January 2009.
Train companies said the revenue would be reinvested, but watchdog Passenger Focus said some rises were unjustified.
Gordon Brown believed it was important customers got "good value for their money", said his spokesman.
Regulated fares - including season tickets - are generally based on a set formula which limits increases to 1% above retail price index (RPI) inflation, although there are some exceptions.
The government's policy is to increase fares above inflation and reduce the contribution from the taxpayer.
The increases are based on July's RPI of 5%, a figure which has since dropped to 4.2%.
However, passengers reliant on Southeastern services between London and Kent and Sussex will see their fares rise by an average of 8%, which is 2% more than the national average.
This is because the company's own regulated fare formula is RPI plus 3%. The firm said it needed extra funds to pay for high-speed domestic services in Kent due to be introduced next year.
Responding to the rises, the prime minister's spokesman said: "It is clear that passengers do have concerns about the value for money they receive from train companies.
"It is a matter for the rail companies to explain why they have made the decisions they have made, but we want to make sure passengers are getting good value for money."
But Association of Train Operating Companies (Atoc) chief executive Michael Roberts said passengers would benefit from the reinvestment, while taxpayers would receive better value.
The changes fall in line with government policy to reduce railway subsidies by 40% between 2006-07 and 2013-14, he said.
Mr Roberts said since 1996 overall rail fares had risen by 5% in "real terms".
Some people would see their ticket prices drop, he told BBC News.
"These fares changes actually mean that 15% of all fares will either be frozen or actually will fall.
"At the same time train companies will be investing in a £800m programme of improvements to trains and to stations, and I think that's actually good news for passengers."
CrossCountry, whose network covers 1500 miles (2414 km) and stretches from Aberdeen to Penzance and from Stansted to Cardiff, has the highest increase for its unregulated fares.
These include advance and leisure bookings, at 11%. By contrast, London Midland has frozen these fares.
Other companies with big unregulated-fare increases are First Capital Connect up an average of 9%, Chiltern up 7.5%, National Express East Coast up 7.4% and South West Trains up 7.2%.
Michael Roberts of Atoc: 'Passengers want to see value for money'
Anthony Smith, chief executive of watchdog Passenger Focus, said it was concerned about the above-inflation rises.
He said: "No fare rises are welcome in the current economic climate.
"Some train companies deserve credit for limiting some unregulated rises. However, rises way above inflation are unjustified and unfair.
"These average fares will no doubt mask some very steep rises on particular routes."
Calling for the government to become more involved, he added: "We also need to look closely at establishing a fairer link between fares, investment and satisfactory performance.
"We cannot simply go on dumping costs on to the passenger in this way."
Union leaders and opposition parties said the government should have intervened.
Gerry Doherty, leader of transport union TSSA, said: "If every other business is cutting prices, why should the rail companies be allowed to get away with daylight robbery?"
Shadow transport secretary Theresa Villiers said the government had let down passengers by failing to provide them with "value for money".
Passengers were putting up with "crisis levels of overcrowding as well as rising fares", with the most packed trains running at over 170% capacity, she said.
The Liberal Democrats called for a freeze in regulated rail fares for a year, to be paid for by cuts to the roads-building budget.
It suggested the government should compensate train companies so that passengers who bought unregulated fares were not penalised.
This week the Transport Secretary Geoff Hoon asked train companies to bear in mind the current economic climate when calculating the new fares.
The Department for Transport said the government worked with train operators to simplify the ticketing system.
A spokesman said the capped, regulated fares accounted for almost two-thirds of all rail journeys.
"We've also committed £15bn to support the railways in the next five years - including a £10 billion investment to increase capacity," he said.
RAIL COMPANY FARE RISES
Proposed changes from 2 January 2009
Avge regulated rise
Avge unregulated rise
Arriva Trains Wales
East Midlands Trains
First Capital Connect
First Great Western
First TransPennine Express
National Express East Anglia
National Express East Coast
South West Trains