Johann Hari: Mayor Boris is a disaster on the two big issues of our day

He is making policy to insulate the very people who caused this crisis

Cripes and golly gosh: it's nearly a year since the outer ring of Londoners booted out Ken Livingstone and installed mop-topped Boris Johnson in the glittering glass testicle of City Hall. Liberal-lefties like me predicted BoJo – with his record of calling black children "piccanninies" and cheering when Bush refused to sign up to Kyoto – would be a disaster. But as far as the media coverage goes, it's been a quiet 12 months. So is Boris a better mayor than we thought? The answer needs to be absorbed across the country, because Boris's London is the test lab for David Cameron's "progressive conservatism" – a hint of what's waiting for us all after the next election.

Let's start with the positive. There have been two unexpected and excellent moves from the Mayor. He knows that most of Britain's half-a-million illegal immigrants have washed up in London, where they live in constant fear, can't approach the police, and face grinding, binding poverty. It's to his credit that he has called for an earned amnesty that will allow these people – who skivvy for us, and keep London's wheels turning – to come out of the shadows and live here legally.

He also changed the policy of the Greater London Authority so all its employees and contractors now have to pay their staff the "London Living Wage" of £7.45 an hour. This is the amount you need to earn so you don't fall below the poverty line – and it's made a hefty difference to thousands of people. And there's more: I think Boris's verbal acrobatics are to his credit. He doesn't talk in pre-processed politicsese but in a real, vivid language that doesn't send voters into a coma. The skills that made him an excellent comic novelist and poet make him a good – if odd – communicator.

Yet on the two great challenges of our time that threaten the future of London – the credit crunch and the climate crunch – Boris's policies have been shocking. As a commentator and MP, Boris was one of the most enthusiastic defenders of the deregulation of financial services, saying it would bring "an era of amazing prosperity". Once the model he cheered on began to collapse all around us, he lashed out – at the people who had been proved right.

He declared this winter that the British people should stop "whingeing" and succumbing to "neo-socialist claptrap". He then, astonishingly, became the only British politician I know of to continue to defend the "the sub-prime sector", saying: "These products allowed millions of Americans to own their own homes." When I read this quote to Paul Krugman, this year's Nobel Prize-winning economist, he said: "Wow. This is economically illiterate. The increase in home ownership by sub-prime mortgages has all been wiped out by repossessions. We're back where we were, only with all the terrible problems you see all around you, and massive debts for the people who took them out."

This isn't just a verbal outburst from Boris. He is making policy – and lobbying the Government hard – to insulate the very people who caused this crisis, and to rebuild their collapsed model. He says the Government's pathetically minor and overdue new regulations on the City are "a vindictive attack on one of the most successful industries in this country". He objects to even the pitifully low increase on the very richest people's taxes by just 5 per cent, claiming it is "not economically sensible". He is fighting to retain the system where Alan Sugar pays a lower proportion of his income in taxes than his secretary.

On the climate crisis, he is worse still. Until he ran for mayor, Boris opposed every single move to prevent the destabilisation of the climate, saying George Bush's trashing of Kyoto was "good for the world". But, like David Cameron, on the road to elected office he claimed to have a Damascene conversion and pledged "a greener, cleaner London". We need one, since this city is highly vulnerable to rising sea levels. Since millions of us live on flood plains, after Hurricane Katrina the London Assembly investigated our flood defences – and found many are "appalling."

But Boris in power has been true to his core beliefs. He has done everything he can to encourage car use, and binned Ken Livingstone's carbon-reduction plans. He has halved the size of the environment team, scrapped the expansion of the Congestion Charge to west London, postponed indefinitely the expansion of the city's "Low Emission Zones", and cancelled Ken's plans to charge ultra-polluting SUVs an extra £25 a day. Despite constantly inviting photographers to snap him on his bike, he has hacked £27m out of the budget for building cycle lanes, wrecking proposals for 300 new ones.

The political symbolism is exposed as a sham by the political reality. Other than planting a few trees, his environmental policy has been "totally appalling", according to Darren Johnson, the excellent Green member of the London Assembly.

And Boris is formulating all these policies as a part-time Mayor of London. He apparently can't live on a mere £130,000 a year, a wage that puts him in the top 0.5 per cent of British people, and 0.0001 per cent of human beings. So he makes two-thirds of his income not from the electorate but from the Barclay brothers, the mysterious right-wing billionaires who live as tax exiles on their own private island. They pay him for a weekly column in The Daily Telegraph. But doesn't London – especially at this time – deserve a full-time Mayor, accountable to us?

Boris has made other decisions that suggest darker policy decisions to come. He has appointed as his director of policy a journalist called Anthony Browne, who has claimed "there is little British left" about London, and that "Britain will be a foreign land" soon. He has raged against "the growing social fragmentation of Britain under the weight of Third World colonisation," blaming immigrants for spreading deadly diseases. His writings recycle preposterous urban myths as fact, like the claim that councils were banning black bin bags as "racist".

Browne has enthusiastically posted on a far-right US website V-Dare, named after Virginia Dare, the first English child born in the New World. The site is dedicated to exploring "whether the United States can survive as a nation-state" in the face of "mass immigration and affirmative action". The British National Party's member of the London Assembly, Richard Barnbrook, said of Browne's appointment: "I cannot help but think that this is at least a step in the right direction." Browne is now the main hand guiding Boris's policy-making.

What does all this suggest about how David Cameron would govern Britain? Like Boris, Cameron claims to be "a new kind of Conservative", committed to environmentalism and "a more moral capitalism". Like Boris, he claims to have undergone a Damascene conversion: until 2005, he was a standard right-wing backbencher who cheer-led deregulation, and whose only statement on green issues was to mock wind farms as "giant bird blenders".

The evidence from London suggests that, given power, he will make a few concessions to modernity on the margins – and regress to rampant right-wingery on the core issues. As George Osborne said cheerfully in 2002: "We have a lot to learn from George Bush's compassionate conservatism."

j.hari@independent.co.uk