The situation faced by passengers using Northern rail services is totally unacceptable, Downing Street has said.
Transport Secretary Chris Grayling is expected to make a statement to MPs later as cancellations and delays continued despite the introduction of temporary timetables designed to halt the disruption.
The Prime Minister's official spokesman said: "We have tremendous sympathy with everyone who has had their rail journey delayed or disrupted.
"What we have seen had been totally unacceptable."
Northern launched an eight-week interim timetable on Monday, removing 165 trains - 6% of services.
Areas affected include Manchester, Liverpool, Blackpool and the Lakes Line between Oxenholme and Windermere.
Govia Thameslink Railway (GTR) - which consists of Southern, Thameslink, Great Northern and Gatwick Express - is also running a temporary timetable enabling passengers to "arrange their journeys with greater confidence".