The cost of running Britain's ailing rail network has doubled, according to the company created to replace Railtrack.
Network Rail is in charge maintenance
Network Rail said spending on the railways in the next three years would be more than £6bn a year, compared with the £3bn originally expected.
The figure will fuel speculation that the cost of keeping the network going is spiralling out of control.
It is also likely to feed through into ticket prices as Network Rail charges train operators more to use its track.
In its business plan, published on Monday, Network Rail said spending on the railways in 2001-06 would be £27bn.
That compares with a figure of £16.7bn allowed for this period by Rail Regulator Tom Winsor.
Mr Winsor will now have to take the revised figures into account as he prepares a report detailing how much Network Rail can charge the train operators.
Network Rail chairman Ian McAllister said: "It is now six months since Network Rail acquired Railtrack Plc and all our experience since then has confirmed our initial analysis.
"Britain's rail network is suffering from a huge legacy of under-investment."
He went on: "We have a fragile network that has been starved of a steady rate of renewals for many years, resulting in poor performing infrastructure that needs more maintenance to carry ever more traffic.
"Network Rail is here to address the problem this legacy has left.
"Action is being taken, but time and patience is needed to see the changes we're making deliver results."
Mr McAllister said it would take up to five years and cost £27bn to clear up the backlog of repairs and improvements that has built up.
Network Rail, which is a not-for-profit organisation, said track maintenance work had got so far behind that a "bow wave" of renewals had arrived and needed to be addressed.
In 12 years a backlog of up to 4,000 miles of track maintenance had built up.
Mr McAllister said he was determined to turn the problem around.
But he added: "It will take time and although we have an unwavering commitment to driving down costs, the network simply needs large-scale investment to replace worn-out assets.
"We recognise that the current costs are unaffordable in the long-term.
"We must be prepared to challenge the assumptions behind the costs, ensure they are robust and strive to deliver even more efficiencies where possible."
The business plan sets out a string of targets for Network Rail, allthough all of them are less stringent than the ones set for Railtrack last year.
The targets include:
- 21% reduction in delays caused by Network Rail
- 39% reduction in broken rails
29% reduction in temporary speed restrictions
The organisation said its delay target was based on the assumption that train performance could return to the levels of 1999-2000 by 2005.