Anglia Railways has admitted that passengers on trains between Norwich and London are suffering as air conditioning systems fail during the humid summer.

Users of the inter-city line have experienced uncomfortable journeys as the equipment sturggled to cope with soaring temperatures.

Up to 15% of carriages are becoming uncomfortably hot when the cooling units fail in service.

Regular passenger Hilda Meadows, who travelled from London to Norwich, said the air conditioning problems had made the journey very uncomfortable.

We have been doing what we can to make the air conditoning as reliable as possible

Anglia Railways' spokesman

She said:"It was sweltering hot and the temperature in the compartment was very close and sticky with hot sun shining in.

"We like Anglia trains but this is not worthy of Anglia's reputation. They really do need to sort it out."

Anglia Railways' corporate affairs director Jonathan Denby said the company had spent money on repairs but it was a never-ending challenge.

He said:"We have been doing what we can to make the air conditoning as reliable as possible.

"We spent more than �100,000 over the winter upgrading the air conditioning systems."

He admitted that a long-term solution might be difficult to find.

"The vehicles are 30 years old and the systems are not as modern as the ones you would install now. They don't cope as well," he added.

"We are getting longer summers and more temperatures above 25C."