RMT also demanded that Transport for London drop its 'madcap' plan to privatise the extended East London Line when it re-opens in 2009.

The call comes as London Underground's third report on the PPP says the private sector has "unacceptably failed" to deliver on key targets.

"This isn't about companies needing to pull their socks up or try harder, this is about the need to end an expensive scam that has lined the privateers' pockets with £2 million of public money every week," RMT general secretary Bob Crow said today.

"The PPP remains a means for doling out guaranteed, risk-free profits to the lucky contractors, and Londoners and Tube workers are suffering as a result.

"Taxpayers' and Tube users' money that should be invested in improvements is being taken out at the rate of £100 million a year, and it has to stop.

"The PPP needs to be brought to a speedy end and the engineering work brought back in-house, but TfL should also drop its madcap plan to put the extended East London Line into the privateers' hands in 2009.

"All our experience and report after report have shown us that privatisation has failed by every measure, and it is unbelievable that TfL should even consider throwing the East London Line to the wolves as well," Bob Crow said.