Greater Anglia has insisted that delays to introducing its new trains are not the cause of problems on rural and cross-country services in the region.
Councillors representing communities on the line between Ipswich and Cambridge say many trains have been replaced by single-carriage trains, or cancelled altogether because existing trains have been sent to Wales.
However a spokeswoman said only four trains had left the region, while 11 new trains had been introduced serving lines from Norwich.
There had been a number of technical faults and accidents with hitting objects on the line - including a collision with a herd of deer - that had forced some trains to be repaired
She said: "We apologise to those customers who have been affected by services operating with shorter trains than normal. We know how important it is to our customers that they have a seat."
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