If there is any way we can go back to court to stop this we will, because I believe Londoners' lives are at risk

Ken Livingstone

He said it could lead to the sort of crisis that has engulfed the privatised rail network.

Transport Secretary Stephen Byers also got a rough ride from Tory, Liberal Democrat and Labour MPs as he defended his decision to back the PPP scheme.

He claims it is the best way to attract the �16bn of new investment he says is needed to revamp the crumbling transport system and provide faster and safer trains.

Mr Byers said an Ernst & Young review provided evidence that the plan represented value for money.

Legal challenge

But Mr Livingstone, who together with transport commissioner Bob Kiley will eventually take over the running of the system, urged a rethink.

"If there is any way we can go back to court to stop this we will, because I believe Londoners lives are at risk," he told BBC News.

He claimed that Ernst and Young had a conflict of interest and that its report had been based on subjective information.

Mr Kiley: PPP 'nightmare version of Railtrack'

Every independent study into the PPP had pointed out how expensive and potentially unsafe it was, he added.

He also attacked the government for "stifling debate" for not allowing himself or Mr Kiley access to crucial documents on the deal until Monday.

Mr Livingstone wants a bond scheme to finance �13bn of improvements to the ailing network.

There will now be a three week consultation period. If the decision is confirmed there would then be a three month handover period.

Shadow transport minister Eric Pickles, during exchanges in the Commons on Thursday evening, said the "off balance deal" bore "all the hallmarks" of Mr Byers - "It's wildly optimistic, it completely disregards dangers".

Pointing to the 1900 timing of the statement, he said that was a time used for matters of war or catastrophe and added: "This is the first time that an impending catastrophe has been made at seven o'clock."

For the Liberal Democrats, Tom Brake said: "This represents for the Labour Party their poll tax on wheels and it is going to haunt them for 30 years."

Labour MP Diane Abbott said imposing the plan against the wishes of Londoners showed "breathtaking arrogance".

MPs opposed

Earlier this week MPs on the transport committee warned PPP would lead to costly contract disputes.

And transport commissioner Bob Kiley has also warned against PPP.

The contract itself is a horror show and it will be creating a precedent for the next 30 years

Bob Kiley

He said the government was trying to impose a "nightmare version of Railtrack" with an unaccountable chain of command responsible for the infrastructure.

He predicted safety problems, managerial chaos, staff tensions and possible legal action.

"Forecasting the amount of body bags is not a good idea."

But he said they had to be sensitive to the safety issues.

"The contract itself is a horror show and it will be creating a precedent for the next 30 years," he said.