Rail commuters have been hit by a double whammy after some station car parking charges were increased above the rate of inflation following the New Year hike in fares, according to a study.
The Transport Salaried Staffs Association (TSSA) said passengers were suffering "daylight robbery" as they returned to work after the festive break to be hit by rises in travel.
Commuters in the South of England have been hardest hit, facing rises above the current inflation rate of 2.1%
TSSA general secretary Manuel Cortes said: "This is little more than daylight robbery by the private rail firms. Passengers have been caught in the crossfire because bosses are determined to get around the Government's cap of 3.1% on rail fare rises, and squeeze yet more money out of them.
"Passengers may have escaped the bullet of inflation plus increases last week but they have now been hit by another bullet-car parking rising higher than the rate of inflation. There can be no justification for these increases at all when wages are rising by less than 1%."
The union called for car parking charges to be included in the regulated rail fares formula which is set by ministers.
Passenger Focus acting chief executive, David Sidebottom, said: "Passengers will see this as a back-door rise hitting them just after the new year fares increase.
"Less than half of passengers are satisfied with car parking facilities at stations, but as they are not regulated they can be a soft target for train company price hikes. If charges have to go up we would hope to see some of the money spent on improving facilities for passengers."
A First Capital Connect spokesman said: "First Capital Connect has in fact kept its station car park prices to around the rate of inflation, reducing some in real terms and freezing others. Off peak and weekend tariffs have also been held and haven't been increased since 2008."
A South West Trains spokeswoman said: "Annual and monthly car park season tickets, which are those used by frequent rail travellers, are increasing by an average of 1.2% (£1.14 per month) and 1.5% (39p per week) respectively.
"Daily and weekly tickets have risen by an average of 3.8% (23p) and 3.5% (21p per weekday).
"The income helps fund additional spaces and car park security measures for commuters."
A spokesman for Southern said: "Revenue from car parks continues to be reinvested in facilities and additional capacity. We have invested over £8 million in improving our car parks, and have to date provided over 1,100 additional spaces."
Paul Watters of the AA said: "Yet more increases in the cost of railway station parking reinforces the impression that, what the rail companies can't get from fares, they will try to get from commuters and travellers who need to turn up by car.
"A 5% hike adds £1.75 to a £35 weekly parking charge, equivalent to a 3.5p-a-litre increase in the cost of filling up at the petrol station. Many commuters, paying typically £3,000 to £4,000 for their annual train season ticket, already pay well over a £1,000 more to park their cars at the station.
"Another £50-£100 to leave the car may be icing on the cake for the rail companies, but pumping up these charges by more than inflation is pure gluttony.
"Public transport strategists talk long and loud about inter-linked travel but car drivers, who are most flexible in getting themselves to public transport hubs, are often the most discriminated against when public travel costs go up."
Rail Minister Stephen Hammond said: "I understand the need for train operators to continually invest in parking facilities but I would urge them to show restraint when it comes to increasing charges and recognise the pressures faced by hard-pressed passengers."