The Government is concerned that Christmas train services could be disrupted by staffing shortages, the rail minister said.
Lord Hendy told MPs that Department for Transport (DfT) officials will continue to examine the issue throughout the festive period.
Many train drivers and other crew members do not have Sunday working included in their contracts, with numerous operators often relying on them volunteering to work extra paid shifts to run timetabled services on that day.
This regularly causes the cancellation of hundreds of trains across Britain, such as on Father’s Day or the day of a major England football match.
Giving evidence to the Commons’ Transport Select Committee, Lord Hendy said the Government is worried about “staffing of Christmas services”.
“That we are concerned about with several train operators, exacerbated by the fact that inevitably the closures close parts of the railway and put more pressure on others.”
He added: “I’ve been through this a lot with Alex (Alex Hynes, director general for the DfT’s rail services group) recently and will continue to be into, right up to and over Christmas.”
Mr Hynes said: “Generally as a system, we’re over-reliant on overtime working for train crew.
“That’s a risk, which may be worse at Christmas time than other times.”