The PPP will improve safety through massive investment in infrastructure

London Underground document

This, they say, will enable every Tube train to be replaced and stations to be modernised.

But details of the plans come less than 24 hours after the High Court gave London Mayor Ken Livingstone the go-ahead to challenge the government's policy.

A High Court judge gave the mayor's transport authority, Transport for London (TfL), permission on Tuesday for a judicial review of the PPP plans.

The hearing will start on 12 June and follows weeks of fruitless negotiations with ministers.

Mr Livingstone and London Transport Commissioner, Bob Kiley, claim PPP would put lives at risk on the Underground and would be too expensive.

Speaking to BBC News, Mr Kiley said: "When you separate out care of the infrastructure from the actual running of the trains, which is what happens under PPP, you are raising the risk element unacceptably."

PPP 'will deliver'

But a document from the Department of the Environment, Transport and the Regions (DETR) says PPP will deliver the "massive investment" needed for the Tube.

Ministers also believe it is better value for money than the existing system.

Mr Kiley accused ministers of being stubborn

Under their plans, responsibility for tracks, signalling and tunnels would be carved up between three private sector companies.

According to the DETR document, the only alternative to PPP is a 13% rise in passenger fares.

It adds that contracts with the private sector will ensure there is a firm timetable for the introduction of new trains and the modernisation of stations.

There are also plans for extra services on nine of the Tube's 12 lines.

Improved safety

The document pledges that safety will not be undermined as a result of the partial sell-off.

It states: "The PPP will improve safety through massive investment in infrastructure. Modern equipment will produce higher safety standards."

Lawyers for Transport for London are expected to argue in June that PPP will undermine safety and will be poor value for money.

Mr Kiley accused ministers and officials of being stubborn in pressing ahead with their plans.

But he added: "Most lawsuits are settled this does not have to get to a judge. If it does we are confident we can prevail."

"I hope we can settle it before the election because time is of the essence here."