A Lib Dem peer has challenged the government's sums on funding for London's controversial tube part-privatisation.

Lord Ezra highlighted growing concern in the capital that the unpopular public private partnership for the London Underground is cash starved.

The peer expressed alarm over speculation that London's long-suffering commuters will carry the can for what many outside government regard as a botched scheme.

"Several bodies, including the GLA, have said that in their opinion the funding for the London Underground is too little. It has been alarming to hear that the shortfall may be made up by a 25 per cent rise in fares," he said.

Ezra was set to tell the Lords that the travelling public should not be made to pay the price of privatisation - either in higher fares or reduced health and safety.

"It would be ridiculous to make the public pay for a flawed system. Fares should not rise by more than inflation, and preferably not at all," he said.

"Ministers must also reassure the public that there will be robust maintenance and safety measures on the tube following the tragic incident at Potter's Bar."