The vanity projects that the Mayor must kill off

When, next month, the full report comes out, and the GLA's new cost-cutting chief executive, Tim Parker, starts work, we will see that second essential revolutionary moment: the part when selected victims are led out to the firing squad. It will be politically correct London's equivalent of the credit crunch and, with any luck, it will be goodbye to the groundbreaking cycling-for-the-blind initiatives, farewell to the gay Bengali workplace sustainability forums.

OK, I made those two up but I make no apology for expecting big changes. Our unemployment and child poverty rates are the highest in Britain. Literally within sight of the City, Europe's greatest concentration of wealth, is Tower Hamlets, where almost 60 per cent of the population is economically inactive. But the LDA has squandered fortunes on vanity projects while making no significant progress on its core mission, of bringing jobs and opportunity to excluded Londoners.

In other areas, there has been achievement but at a cost surpassing all reason. Bus use under Ken rose by 45 per cent - yet subsidy rose by more than 1,000 per cent. So waste was a defining characteristic of the Livingstone mayoralty, and there are plenty of kittens that will have to be drowned. But it has to be done in the right way.

To avoid the inevitable charge that Boris is dismantling the public services, the utter worthlessness of the projects that need to be culled must be made very clear. TfL is, for instance, proposing to spend £ 40 million on two so-called "transit" schemes in east and south-east London. These turn out to be nothing more than new bus routes, running almost entirely on existing roads, indistinguishable in every meaningful way from the buses that already run there.

Above all, and in keeping with the new Cameronite orthodoxy, the savings Johnson makes should on no account be used to cut tax. The proportion of GLA income derived from the council tax is small. The amount Boris could give back to council taxpayers would be almost too small for people to notice.

Most of the GLA's funding comes from central government. So Johnson needs to be extremely careful that his cuts do not simply give Whitehall the excuse to claw back his grant.

The GLA should, and will need to, allocate every penny of the cash it saves for things that really are worth spending money on. Crossrail is going to be incredibly expensive. Youth programmes and anti-crime projects will have to be paid for. And the economic slowdown can only increase the need for an effective LDA.

Boris, in other words, should slash. But he shouldn't burn.