Network Rail chief executive Mark Carne has admitted that the cost of electrifying the Great Western Main Line will be £1bn higher than previously forecast.
The revelation came as Mr Carne faced a grilling from MPs on the public accounts committee as part of an inquiry into the operator’s handling of the £38.5bn Control Period 5 investment programme.
Mr Carne said electrification of the line to Swansea will cost £2.8bn, up from the £1.6bn estimated last year.
The new estimation is also nearly £2bn higher than the £874m figure given in 2013.
The chief executive also indicated that work on the line was behind schedule and would not hit its scheduled completion date of 2018.
The revelations came during a heated hearing in which Mr Carne, alongside Office of Rail and Road chief executive Richard Price and Department for Transport permanent secretary Philip Rutnam, were all questioned about their roles in the planning of CP5.
Mr Carne sent a letter to committe chair Meg Hillier two hours before the meeting in which he revealed the new cost.
Ms Hillier said she found the significant increase in cost “staggering”.
Responding to this, Mr Carne said: “Our cost estimates were wrong, fundamentally they were wrong.
“Electrification costs as a whole have increased quite significantly compared to the estimates made at the time of the final determination last year.”
When asked by Ms Hillier whether he had an idea about how much the total overspend would be, Mr Carne said that “he could not come up with a definitive number”.
Mr Carne and Mr Rutnam also told the inquiry that it was likely the Great Western project would not meet its expected completion date of 2018.
Currently, the line from Newbury to Bristol Parkway is expected to be completed by 2016, with electrification from Bristol to Cardiff and then Swansea expected in 2017 and 2018.
However, Mr Rutnam said that it was currently well behind that schedule.
He said: “I’m afraid I am not in a position to give a schedule for the completion date for the Great Western Main Line electrification.
“It is highly likely that there will be delays to that schedule and I’m afraid at the moment I can’t give a new schedule at the current time.”