The Rail Maritime and Transport Union (RMT) said Metronet and Tube Lines, the firms responsible for maintaining the network, had "spectacularly failed".

A government spokesman said that by 2017 PPP will have delivered £16bn of investment for the Tube.

Transport for London (TfL) said it had done all it could to make PPP work.

"It is imperative that the government continues to support and finance the renewal of the Underground" - TfL spokesperson

A spokesman for the government said that during the course of the contracts almost 250 stations would be refurbished, more than 300 new trains would be brought into service and 80% of the track would be updated.

"We have also provided the Mayor of London with the transport funding needed for the Olympics," he said.

But the RMT said warnings that PPP would turn out to be an "expensive failure" had come true.

It said Metronet and Tube Lines had been given £3.3bn of public money and made £300m in profits "but by anyone's standards... they have failed to deliver".

'Vital improvements'

RMT general secretary Bob Crow said the move had resulted in "deterioration in service, missed targets, infrastructure failure, engineering overruns, an alarming increase in safety problems and a massive increase in costs."

Mr Crow added that the government must "bring the necessary legislation forward to end the PPP and return the Tube's infrastructure to London Underground".

A TfL spokesperson said: "TfL's position on the PPP is clear. It is not the system we would have chosen to finance and manage the renewal of the Tube. But once the government transferred the Underground to TfL under PPP, we have done all we can to make it work.

"What is vital is that the major capacity improvements - the line upgrades - due from 2009 onwards, are delivered by Metronet and Tube Lines on time and on budget.

"It is imperative that the government continues to support and finance the renewal of the Underground."

Metronet did not wish to comment.

See also:

Union call to end Tube PPP deal

Press Association: December 31, 2006

The country's biggest rail workers' union has called for the "disastrous" public private partnership (PPP) to be scrapped, on the fourth anniversary of the controversial scheme to finance improvements on the London Underground.

The Rail Maritime and Transport union said warnings that the PPP would turn out to be an "expensive failure" had come true.

Metronet and Tubelines, the two groups in charge of maintaining and upgrading the Tube, have been given £3.3 billion of public money and made £300 million in profits, said the union.

"By anyone's standards they have spectacularly failed to deliver," said RMT general secretary Bob Crow.

"The privatisation and fragmentation of Tube maintenance have resulted in deterioration in service, missed targets, infrastructure failure, engineering overruns, an alarming increase in safety problems and a massive increase in costs.

"By contrast, the national rail network has brought maintenance back in-house and is already reaping the benefits in increased efficiency and better safety.

"Time is rapidly running out, and if we are to have a world-class Tube network in time for the Olympics it is no longer an option for the Government to allow the PPP to rumble on towards disaster.

"Today is the day for New Year's resolutions, and one of the Government's must be to bring the necessary legislation forward to end the PPP and return the Tube's infrastructure to London Underground."

The Department of Transport said: "By 2017 the PPP will have delivered £16 billion of investment in maintenance and modernisation of the Tube.

"During the course of the contracts, almost 250 stations will be refurbished, more than 300 new trains will be in service and some 80% of the track will be replaced or refurbished, with all lines receiving modern signal and control systems. In all, the capacity of the network will increase by 25%, including a 45% increase in Jubilee Line capacity by the time of the Olympic Games."