Byers: Choose plan B

What might "Plan B" look like? If the Government took the decision to kill off the PPP, a replacement scheme would be needed to rebuild the Tube.

Ken Livingstone and Bob Kiley long ago published proposals involving public sector control over the investment programme. But their scheme also needed to be underpinned by bond-financed borrowing, which the Chancellor is opposed to.

The most likely replacement for the public-private partnership would be to transfer responsibility for the Tube, including all its tunnels, trains and the other hardware currently the subject of the PPP, to Mr Livingstone and Mr Kiley.

Instead of bonds, the Government would give the Mayor most of the funding that would otherwise have gone to paying the PPP companies. It would then be up to him to decide how to refurbish the Underground.

But there would be an obvious drawback to this option. Scrapping the PPP and starting all over again could further delay the start of any improvements to the Tube. Notwithstanding all the criticisms of the PPP, the two remaining bidding consortia - Tube Lines and Metronet - have done a massive amount of work preparing to take over the Underground. To dump all this expertise would be plain daft.

So there might be a compromise. The Government could agree to allow the Mayor and Mr Kiley to decide the phasing of works and determine the details of the contracts. They, in turn, could agree to accept many of the investments planned by the consortia in track, signals and trains.

There could be problems with the precise form of the new contracts (which would be between the Mayor's Transport for London agency and the consortia) because of the complex, incentive-driven proposals in the contracts as they now stand. But lawyers - at a price - could undoubtedly find a way of stitching things together.

If the Government had really decided to kill off the PPP, the private consortia would, presumably, still prefer to get new contracts from Ken Livingstone than no contracts at all. Mr Livingstone, for his part, would be in the position of controlling both the Tube's assets and staff.

However, the real winners from such a solution would be the people of London and, surprisingly, Transport Secretary Stephen Byers. The former would finally be able to hold their Mayor directly to account for the state of the Underground, while the latter would be rid of any responsibility for it. Do yourself a favour, Mr Byers. Choose Plan B.

? Professor Travers is director of the Greater London Group at the London School of Economics