A budget rail ticket popular with people wanting cheap days out to London will rocket in price by more than a quarter next month.

Chiltern Railways’ super off-peak return from Birmingham Moor Street to the capital is set to rise from £19.50 to £25.

The operator has blamed rising fuel costs for the price increases but said it was raising its cheapest tickets to protect commuters.

Passenger groups have said the fare increase will hit leisure passengers unfairly.

“Chiltern has always been better value than Virgin and have always sold themselves on that even though it’s a slower service,” said Kevin Chapman of the West Midlands Campaign for Better Transport.

“Fuel is an issue but this is a poor time to choose to do something like this because people are struggling financially.

“I would be very surprised if they were to drop the price should fuel come down.

“Ultimately their passengers will have to take a look at the cost and decide whether it’s cheaper to just drive to London.”

The new fares will come in to effect on May 22 but will not affect any other tickets.

Chiltern said it faced paying an extra £420,000 in fuel costs between now and the end of the year but had protected itself against any future surges in oil prices by buying bulk diesel in advance.

The operator’s marketing boss Thomas Ableman said: “We know that fare increases are never popular, but we need to ensure we are covering the costs of running the railway.

“We do not receive any Government subsidy, so these increased costs can only be paid by our passengers.

“By only increasing the super off peak fare, we can ensure there is no impact on our commuters and that Chiltern Railways remains a great value choice for travel.”

Chiltern will next month introduce brand new carriages costing £1.2 million each.

The new carriages will be the most fuel-efficient on the network, helping to reduce exposure to future fuel price increases.