The part-privatisation of the London Underground is not certain to bring the improvements that were promised, a government spending watchdog has said.
Marked improvements are not likely before 2007, the NAO says
The National Audit Office (NAO) said the first year of the private-public partnership (PPP) had mixed results.
Its review into the PPP deals and their likely effectiveness also said the scheme was expensive to set up.
Transport Minister Tony McNulty told BBC London he believed PPP will give the capital the tube "it deserves".
The NAO said that, compared to London Underground's (LU) pre-1997 investment regime, PPP offered "an improved prospect, but not the certainty, that the infrastructure upgrade will be delivered".
Passengers could expect only marginal improvements in the first seven-and-a-half years of PPP, with most improvements coming after 2007, it said.
It went on to say that work began two years later than planned and recovering the maintenance backlog would take 22 years rather than the projected 15 years, with drawn-out negotiations seeing the cost of the deal rise by £590m.
Meanwhile, a LU report said key parts of the service had not improved since it was part-privatised.
Engineering over-runs and inadequate planning had hampered the Tube, it concluded.
But LU said there had also been improvements such as cleaner stations and less graffiti on trains.
And the thousands of obligations in the contracts prompted the NAO to ask: "Are the parties clear about their responsibilities?"
It gave the example of a dispute over who was financially responsible for repairs to faults with the bearings on Piccadilly Line train axle boxes.
The NAO noted "low productivity" during weekend closure work by the infrastructure companies, with 226 delays in the first year of PPP caused by companies handing back the track late after doing work on it.
Mr McNulty, MP for Harrow East, said there needs to be progress: "There have been teething problems of course. It's such a complex deal.
"We need to bed the down the deal and that the PPP can deliver far more than it has done in its first year."
The review assessed the first 12 months of Metronet and the first 15 months of Tube Lines, the latter firm having completed its signing of PPP contracts earlier.
The chief executive of Tube Lines, Terry Morgan, said: "We have made substantial progress during our first year with a reduction of 30% in the number of incidents.
"However, the report rightly identifies that we have faced significant performance challenges and that it will take time to turn around LU network."