.
Transport Secretary Patrick McLoughlin said rising costs and missed targets made an existing £38.5bn investment plan untenable,
Mr McLoughlin said Network Rail should have foreseen the improvements would cost more and take longer.
Network Rail said the plan, which was launched last year as the "largest modernisation of the railways since Victorian times", was too ambitious.
Under the changes, the government said electrification work on the Midland main line and on the Trans-Pennine route between Leeds and Manchester would be "paused".