Mr Ottaway said: 'The report, by Glaister, Scanlon and Travers, is as damning as they come. It makes clear that the government's plans are not viable.'
The report states that 'the government's plan for the public private partnership (PPP) for the Underground is flawed in principle, and impractical ... Before it is too late, the government should alter its plans and modify the GLA Bill to allow the new mayor and assembly the freedom to choose the best solution from among a range of available alternatives.'
Mr Ottaway said: 'We agree. It confirms our view that the GLA will be lumbered with an inflexible debt for more than 30 years with little prospect of being able to re-pay it or that the mayor will have any say in the investment strategy.
'It's ironic that this report comes out just days after the privatised railways announce a£27bn investment programme. At the same time, railway fares are falling in real terms. Publicly-owned London Underground has rising fares, low investment and an uncertain future. What a contrast!'