Commuter Melanie Whitehouse is furious after discovering by chance she was paying too much for her train journeys.

Miss Whitehouse travelled on the Thameslink route between Brighton and Blackfriars in London three days a week for about two months.

To avoid queuing, she bought her ticket from a credit card machine at Brighton station, which is managed by Connex, paying £14.60 for a day return.

She was dumbstruck to find she had been paying £2.60 a day too much when the credit card machine broke down and she was forced to buy a ticket from a kiosk.

Miss Whitehouse, 39, who lives in Brighton, said: "When I came to pay, it was £12.

"The man behind the counter said it was because the credit card machine didn't have the facilities to make reductions on tickets.

"He said it couldn't be changed for discounts.

"It does not say anywhere in the station that it is more expensive to buy a ticket by credit card than if you queue up. It makes me so angry. If you ask questions you don't get anywhere and Connex and Thameslink have a totally uncaring, rude attitude."

She accused Connex, which sets the fares at Brighton, of keeping customers in the dark about reductions and making the system deliberately complicated.

Miss Whitehouse added: "I was paying too much for a service which is extremely unpleasant. We are forced to travel up to Blackfriars on these Thomas the Tank Engine trains. You end up with cramp in your legs and the toilets are disgusting.

"I often feel sorry for those poor tourists who get on at Gatwick and are forced to stand up. They must think they have arrived in a developing country."

A spokesman for Connex admitted the credit card machines could only offer limited travel options and these were not always the cheapest.

He said: "The machines are limited with the options of tickets they can sell because there is not enough space to offer every possible combination of tickets.

"We have to comply with the Rail Regulator who has an impartial selling requirement - we cannot promote certain tickets above others.

"We only take the top 20 destinations.

"This lady was getting an all-London destinations ticket but when she went to the ticket office they have quite rightly told her the cheapest fare for the journey she wants to make.

"We are looking at installing new types of machines that give more space to be able to offer more options."