The price of electrifying railway lines between Sheffield and Bedford is set to double because of rising costs and delays.
Network Rail is improving key stretches of track to run electric trains instead of diesels.
It is said the cost of electrifying the Midland main line between Sheffield and Bedford will now cost £1.4bn rather than the £650m expected.
Senior industry sources have claimed that delays could also push back the electrification of the Trans-Pennine route between Leeds and Liverpool to 2021 - affecting proposals to connect northern cities in a so-called ‘northern powerhouse’.
Mark Carne, chief executive of Network Rail, said electri–fication costs had risen as the projects had increased in scope and complexity but insisted the deadline would be met.
“This is like open-heart surgery because you are taking a very vital artery and doing work on it,” he said. “We’ve not invested in electrification for 20 years and inevitably when you start on a big process of electrification there’s a learning curve.”
Costs of electrifying lines from London have also risen.