Nearly half of Greater Anglia's rural trains failed to arrive on time during the Christmas period.
In the four weeks to 4 January, 54.9% of those services did not arrive at the station within 59 seconds of schedule, according to the operator's statistics.
Cabinet minister Therese Coffey MP previously criticised the "catastrophic performance" of Greater Anglia's newly-introduced trains in December.
Greater Anglia said it was "very sorry" for the problems in December.
Figures showed that the number of rural services arriving within 59 seconds of schedule dropped by 14 percentage points in December, compared to 69% arriving on time across the previous 12 months.
More than 10% of those services also experienced cancelations or arrived at their final destination more than 30 minutes behind schedule.
In the same month, Ms Coffey had called on the Transport Minister Grant Shapps to intervene following a series of delays and cancellations involving the operator's new trains.
Greater Anglia said those problems were not due to the performance or design of the new trains.
A Greater Anglia spokesman said: "We're very sorry for the problems customers suffered on our branch lines in Norfolk and Suffolk during December, because of signalling problems that led to extensive cancellations, whilst additional safety-related checks and other investigations took place.
"Most routes saw a full timetable restored from 16 December. However, a full timetable was restored on the Norwich to Sheringham line on 23 December, following modifications to some of the level crossings, but with some speed restrictions still in place.
"Following modifications to other level crossings, the remaining speed restrictions were removed on 10 January with an immediate positive effect on performance and all trains running on time over the weekend.
"The knock-on effect of December's signalling issues on the testing and commissioning of our new trains, and the associated driver training programme, has also meant it has taken longer to restore the full Ipswich to Peterborough service. Services have started to improve and we are expecting to operate the normal timetable on that route from next week."