Greater Anglia say this month's major rail disruption is not down to the "performance or design" of their new trains.
Passengers on rural lines in Norfolk, Suffolk and Cambridgeshire have faced weeks of cancelled or delayed services.
They have mostly been blamed on a major signalling fault, with speculation that Greater Anglia's new trains are not interacting with the track signalling system properly.
However, in a statement released on Wednesday, 18 December the train operator defended the design of the trains.
A spokesperson said: “We are very sorry for the major disruption to services on our regional lines recently.
"These delays and cancellations were not due to the performance or design of our new trains.
"We were unable to run our normal train service due to signalling issues.
"We worked round the clock with Network Rail to investigate the cause of the signalling problems, looking at the effects of extreme autumn weather and leaf fall on the signalling equipment, the components of the signalling equipment itself and the interaction of our trains, new and old, with the signalling system."
The company say a majority of rural services have now been re-introduced, with the exception of the Norwich-Sheringham and Ipswich-Peterborough routes.
The disruption has also delayed their driver-training programme, meaning the rollout of the new trains has been set back.
The spokesperson added: "That programme has now resumed and we’re hoping to introduce further new trains on our network soon and restore a full, reliable service across all our regional routes as quickly as we can.”