Metronet will request an extraordinary review of its 30-year contract to upgrade two thirds of London Underground in an attempt to gain at least an extra £600 million in public money, The Times has learnt.

The consortium, whose shareholders are Balfour Beatty, Bombardier, Thames Water, EDF Energy and Atkins, has abandoned hope of reaching a negotiated settlement with Ken Livingstone, the Mayor of London, over its cost overrun.

It believes Mr Livingstone will be forced by the Tube public-private partnership arbiter, Chris Bolt, to pay well over half the £1.2 billion it has overspent in the first four and a half years.

By triggering the review in the next four weeks, Metronet is confident the result will be known before Mr Livingstone seeks reelection in May 2008.

Mr Livingstone, a long-standing opponent of the part-privatisation of the Tube, has repeatedly said that Metronet will not receive “an extra penny” of public money.

Metronet admits that it is partly responsible for the cost overrun on station upgrades and track replacement, but claims the majority of the extra cost is the result of London Underground expanding the scope of its contracts.

It will offer LU a choice between paying extra or cancelling most of the 84 station upgrades it is due to commence between now and 2010.

A Metronet source said: “Ken is deceiving the public by pretending that we can be forced to pay the entire bill for the cost overrun. We want to expose him.”

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