RAIL chiefs have refused to guarantee a key scheme to improve Northern rail services will go ahead – warning the cost is still unknown.

Flagship plans to electrify the trans-Pennine route between York and Manchester – allowing faster, ‘greener’ services – are in jeopardy, an inquiry by MPs was told.

Funding was announced back in 2011 and work has already begun altering bridges on a project described as “vital” for economic growth by Network Rail.

Now the organisation has admitted there is no firm cost for the scheme – and, therefore, a risk that it may yet have to be delayed or scrapped.

Asked if electrification will definitely go ahead, Paul Plummer, Network Rail’s strategy director, told the Commons transport select committee: “I can’t give you that absolute, categorical confirmation.”

An alarmed Louise Ellman, the committee’s chairwoman, said: “This is something we will be taking further.

“I feel concerned that, suddenly, all sorts of questions marks are being put against this. We want to know whether schemes that have been promised are going to be delivered.”

The admission is potentially embarrassing for George Osborne, who has vowed to deliver far more ambitious – and expensive – plans for a high-speed rail line across the Pennines.

Yesterday (Weds, July 2), the Chancellor promised an “action plan” by the autumn, setting out “the route, the timescales and the cost” of the so-called HS3 scheme.

Pledging to “connect up the great northern cities”, Mr Osborne told an audience in Liverpool: “Let me be clear. I don’t want the Northern Powerhouse to be just a grand idea that never becomes reality.”

But, now, rail chiefs have warned they will not make a final decision whether to press ahead with electrification until full costing is known – in March next year.

Currently, the Liverpool to Manchester section is being electrified, a project due to be extended to Leeds and York by December 2018.

But Claire Moriarty, from the department for transport (DfT), echoed Network Rail by warning of “choices to be made” if costs run over budget.

She told the committee: “The Government will decide whether to put more money in, or whether to have discussions about the phasing, or scoping, of the projects.”

Speaking afterwards, Ms Ellman added: “There's no point having spent money so electric trains can run from Liverpool to Manchester, only for passengers to have to change to diesel trains to get to Leeds and York - and then back onto electric trains.”

The DfT sought to play down the possible threat to electrification, telling The Northern Echo: “We are very confident that what we have set out is deliverable.

“We look to the Office of Rail Regulation and Network Rail to ensure costs are kept to an acceptable level and offer value for money for the taxpayer.”