Network Rail has confirmed that floodwater is likely to continue to affect trackside signalling and safety equipment for some time.
In a statement, they said: "While they work to fix the problem we will only be able to run five trains an hour between Paddington and Reading in each direction. This is around a fifth of the services that would normally be scheduled.
"This will continue until Network Rail lets us know it is safe to run a full service again. We strongly advise customers not to travel unless it is absolutely necessary, and to consider alternative routes."
More top news
A 20-year-old man who died in a triple stabbing outside Parsons Green Tube station has been named by police.
David Jones was responding to London's Fire Commissioner who said the term 'fireman' was outdated and should stop being used.
A report published by the Boundary Commission for England details plans to reduce the number of MPs by scrapping 50 constituencies.