PASSENGERS on Britain’s newest trains will be left with “numb bums” from sitting on uncomfortable seats, train drivers warned yesterday.

With new research showing that the average age of Britain’s trains is the highest since records began, operators have trumpeted the introduction of new carriages.

But passengers have criticised new units — including the flagship stock replacing the Intercity 125 trains on key routes — for having hard seats, low armrests and no tables. On top of that, many seats do not line up with the windows.

Drivers’ union Aslef said this was the result of private operators being “concerned only with cramming in as many people as possible.”

General secretary Mick Whelan said: “While the few new trains are lighter and airier, the seats are much less comfortable than on the old stock they replaced.

“They leave you with a numb bum – it’s no wonder passengers are complaining.

“We’re going backwards, not forwards. We need more investment and that should come from the train-operating companies.”