A Labour MP has warned ministers that the buck will stop with them if plans for the partial privatisation of London Underground fail.

During a debate on the government's public-private partnership plans for the Tube, Harry Cohen predicted "endless haggling" over safety issues if the plans go ahead in their current form.

But the government defended its proposals as the "most extensively examined PPP ever".

Cohen, the MP for Leyton and Wanstead, welcomed the government's financial commitment to the Underground, but said he was "disturbed" that there was nothing specific about the plans in the Budget Red Book.

"Does it mean transport ministers did not fight their corner for the London Underground?" he asked.

Cohen told ministers that the PPP "does not seem to give value for money" and would deliver far less than originally envisaged or needed.

The plans would mean no new or refurbished trains on the Central line until 2016, and train frequencies could also worsen, he warned.

The MP cited a series of objections to the PPP, saying it would reduce safety.

Splitting trains from track maintenance would repeat "a key failing of the national rail network" he said.

Cohen also said that in its comparisons of the PPP and the public sector alternative, the government had unfairly adjusted its model to give a five per cent advantage to the PPP.

And by the mid-way stage of the 30 year contract, the private sector "infraco" bidders would be in an effective monopoly situation resulting in them having the public sector "over a barrel" in any disputes, said Cohen.

He also condemned the risk transfer, saying that services could deteriorate to five per cent below current levels and the infracos would still be eligible for bonuses.

Cohen told ministers there was no confidence in their plans.

He said: "There is a huge level of dissatisfaction with it, and a lack of confidence in it."

The Liberal Democrat MP for Newbury, David Rendel, said that the government had "driven a coach and horses through his own regulations" in the bidding process.

He condemned the decision to issue "comfort letters" to the bidders which would reduce the effective transfer of risk.

"That to my mind blows a huge hole in the secretary of state's justification for the PPP," said Rendel.

Conservative Uxbridge MP John Randall also told the government its plans had been rejected by the public.

"Do not stick to the dogma, understand that there is real opposition from all sides," he told ministers. "Its not opposition for opposition's sake, it is based on sounds facts.

"They will have a difficult job trying to sell this to the public, there is very little support for it."

Liberal Democrat MP Edward Davey also predicted that there "will be many London Labour MPs who, in a few years time, will wish the government had never gone down this track".

Shadow transport minister Eric Pickles said the "discredited" scheme should be abandoned.

"It looks more and more like an Enron deal," he said.

Transport minister David Jamieson said the government wanted good value for money for taxpayers and passengers.

There had been "extensive consultation" on the plans, he said, and achieving value for money was "the key objective for the government".

He said the government's proposals were the "most extensively examined PPP ever".

"The government is satisfied they provide that value for money that is so important," he said.

Jamieson denied that the plans would see the fragmentation of the network.