Rail operators are preparing to reduce train timetables over the coming weeks to cope with the predicted loss of staff off sick with Covid.
Thousands of passengers across the UK have faced last-minute train cancellations and delays as cases of the omicron variant continue to surge across the UK.
The Rail Delivery Group, the membership body representing British rail operators, said the decision to cut timetables was "being considered".
The group said sickness levels had reached 8.7 per cent in the seven days to Monday, with one in 20 services across the network now cancelled.
Seb Gordon, the director of external communications at the Rail Delivery Group, said it was "important to prioritise running as many trains as we can, even if that means there’s a few more of those frustrating short-notice cancellations".
He added: "But obviously, as we get further into this wave of the pandemic – which we hope will not materialise in the way that people are anticipating – it may be that we decide actually we need to prepare for a lower level of staffing over a longer period of time and we will reduce the timetable."
Number of Omicron Covid cases in UK
Forthcoming strike action on Christmas Eve by the National Union of Rail, Maritime and Transport Workers has also forced CrossCountry to cancel routes both between England and Wales and across Scotland.
The operator urged customers to avoid travelling this Friday and on New Year’s Eve due to "widespread disruption" arising from the strikes.
It comes as new figures reveal how demand for rail travel has plummeted since the emergence of omicron.
Passenger numbers were at 53 per cent of pre-pandemic levels on Monday, according to preliminary statistics from the Department for Transport – a reduction from 61 per cent the week earlier, and 68 per cent on Monday, Dec 6.
‘This is a situation that is not going to improve’
Other major train operators announced a swathe of cancellations over staff shortages and falling passenger numbers in the final working week before Christmas.
Greater Anglia, which connects London with Essex, Suffolk Norfolk and Cambridgeshire, announced on Monday that it was suspending more than 60 of its services.
"We also have to plan for our staff being affected by the omicron variant, especially as we’re already starting to see the early signs of its impact, to ensure we can continue to provide a reliable service," a statement on the firm’s website said.
Great Western Railway said it had 30 cancellations on services predominantly affecting round trips on the Devon and Cornwall lines due to staff shortages.
A spokesman said that while GWR is currently "coping" with the pandemic, "how that will play out over the next few days and weeks is yet to be seen". He added: "This is a situation that is not going to improve."
The operator said it took the decision due to "rising numbers of staff unavailable to work because of testing positive for Covid and having to self-isolate".
London North Eastern Railway said it was reducing services between London King’s Cross and Leeds and Lincoln as a result "of an increase in the number of our staff self-isolating due to Covid-19".
Avanti West Coast, which covers long-distance passenger services for routes between London, Birmingham, Liverpool, Manchester, Glasgow and Edinburgh, also admitted “there may be some short notice cancellations”.
A spokesman for ScotRail said Covid-related staff absences have impacted services "mainly across the central belt of Scotland, which has seen a number of services cancelled or amended over the past two weeks".