British rail commuters pay up to 10 times as much for season tickets as some European counterparts, a transport pressure group claims.
With UK fares due to rise by an average of 6% next week, the Campaign for Better Transport compared the costs of travelling into London with those in five other European capitals.
Spokeswoman Sophie Allain says the economic recovery is being put at risk.
Train companies said the "flimsy" study focused on just one season ticket.
In his autumn spending review, Chancellor George Osborne capped fare increases to inflation plus one per cent, rather than than plus three per cent as originally planned, by making a government cash injection of £136m.
But even despite that, the CBT found a huge disparity in prices for commuter journeys of similar length into the five cities its study covered - London, Paris, Berlin, Madrid and Rome.
An annual season ticket from Woking to London, including using the London Underground, costs £3,268.
In France, a journey from suburban Ballancourt-sur-Essonne to Paris costs £924.66.
The cost of a season ticket on the 21-mile Strausberg to Berlin route is £705.85, while Spanish commuters pay £653.74 for a season ticket to travel the 22 miles journey between Collado-Villalba and Madrid each working day.
But the biggest disparity comes when the British rail fares are compared with those in Italy. A similar ticket from the Rome suburb of Velletri into the city costs a mere £336.17.
The distance is 22 miles, meaning an Italian who makes the return journey five days a week all year long would be paying just 3p per mile travelled.
"We knew we had some of the most expensive rail fares in Europe, if not the world, but even we were shocked by how much more the UK ticket was in comparison to our European counterparts," said Ms Allain.
Fare rises were affecting the UK's competitiveness, she added.
A spokesman for the Association of Train Operating Companies said the research did not "stand up to scrutiny".
"Next year, the average commuter will pay just over £2,000 a year, or less than £6 a day, to travel to work and back home again by train," he said.
"In many other countries, the state chooses to subsidise the railways more heavily than in Britain."
Bus and tube fares in London will also be going up on 2 January, with the authorities blaming the cost of projects such as Crossrail and Thameslink, which have involved considerable changes to existing facilities, with resulting closures and disruption.
The government is determined that farepayers, rather than taxpayers, bear more of the cost of railway changes.
A Department for Transport spokesman said it recognised the pressure on family budgets.
"That is why we announced that 2012 regulated rail fares will rise by an average of inflation plus 1%, not plus 3% as set out in the spending review.
"Revenue from fares is helping to deliver one of the biggest programmes of rail capacity improvements for 100 years, which will benefit passengers and stimulate economic growth - this includes 2,700 new carriages, a £900m electrification programme and the delivery of major projects like Crossrail.
"Better value for farepayers and taxpayers can only be achieved if the rail industry works together to reduce inefficiency, and we will be publishing our rail reform plans early next year."