Signal problems will cause delays on trains to and from London Waterloo this morning, National Rail warned.
The signalling issues are affecting platforms 11,12 and 13, and planned improvement work at the station means there is already reduced capacity.
As a consequence of the reduced number of lines and platforms available, delays and alterations can be expected to the service, National Rail said.
The rail operator expects the disruption to continue until 12pm.
Commuters have been warned they can expect to wait up to an hour to get on trains at Waterloo this month, as the station undergoes an upgrade to increase capacity so it can accommodate 45,000 extra passengers.
The improvement works got off to a bad start this weekend when a system error caused slow updates on information screens at train stations, and a signal failure led to additional delays between Clapham Junction and Waterloo.
There are also delays in and out of London Paddington this morning.