"This is simply a devastating report for the architect of the Public Private Partnership contract - Gordon Brown.
"It is unforgivable that as much as £410 million of taxpayer's money has been wasted. The PPP deal that was forced on Londoners by Gordon Brown has been totally exposed as a bad deal for both taxpayers and for passengers.
"The report is not saying that the private sector is all bad and that the Tube upgrades can only be carried out by the public sector. The Mayor now needs to ensure that London Underground and Tube Lines work together efficiently so that the taxpayer is not put at further risk and we get the upgrades on time and on budget."
