The model for Ken Livingstone's plans to use bonds to fund the £14bn revamp of London Underground is close to falling apart, seriously threatening the credibility of Mr Livingstone's grand plan for London.
Financial, government and transport experts have told the Metropolitan Transport Authority of New York (MTA) that its latest $16.5bn (£10.6bn) scheme to improve the city's transport system cannot be financed by issuing bonds.
The MTA is now having to go cap in hand to the Governor of New York State, George E Pataki, for state funds to bail out the ailing New York underground.
The financing plans, which proposed the issue of $20bn of bonds - about the same as is needed for the London Underground - have been attacked by the State Comptroller (the US version of the District Auditor), politicians from all sides of the spectrum, local business bodies and Wall Street.
"We are looking at a return to the 1970s, with the MTA running out of money for operations and good repair, and no credible way of financing projects," said Robert Kiley, a former chairman of the MTA, which now runs business group the New York City Partnership.
The MTA has been cited as the model for how Mr Livingstone would finance the regeneration of the tube if he is elected as London Mayor next month.
He has stated his opposition to the Public Private Partnership being pushed through by the Department of Transport, Environment and the Regions.
The PPP involves private companies taking control of the infrastructure of the tube under 30-year contracts. Bids have been put in for two of the three contracts and will soon go in for the third.
However, Mr Livingstone is not deterred by the problems with his model for the tube. "Part of the problem is the amount of bonds they have issued," said Mr Livingstone.
"They have been issuing them for 19 years and have built up a massive debt. If we are still issuing bonds for the tube in 19 years, you can come back and question me about how we can pay for them."
Mr Livingstone claimed that London Underground would only have to issue £2.5bn of bonds immediately and then only £400m a year after that.