Leading article: Gordon and the green giant

Gordon Brown - like the mountain in the French fable - has laboured and brought forth a mouse. His Budget announcement of a £45 increase in road tax for the most polluting cars will do little to stem the damage being done to the environment, and the world's climate, by Britain's gas-guzzlers. The new tax, totalling £215 a year for the most petrol-hungry car, will make little impression on people willing and able to spend up to £60,000 on their motorised leviathans. It falls far short of the £1,000 imposed annually by Ireland and some other European countries on such vehicles, and is put to shame by the supposedly environmentally irresponsible Chinese, who last week slapped a 20 per cent sales tax on them. We were given the impression that the Chancellor would use the Budget to accelerate the country towards greener motoring; instead he has stalled in third gear.

But it would be wrong to heap too much blame on the Prime Minister in waiting. The biggest villains are the Secretary of State for Transport, Alistair Darling - along with his anodyne junior minister, Stephen Ladyman, who last month denounced green motorists as "salad eaters". They have set their faces against any big increases in the tax - and indeed against any suggestion that their department take serious steps to combat the global warming that the Prime Minister describes as the most serious long-term problem facing the world.

At least Mr Brown is moving in the right direction. After many years when he showed little interest in the environment (despite promising before taking office to be the "greenest" Chancellor ever), he is becoming increasingly engaged with climate change. He realises that the period when he hopes to be prime minister - running up to about 2013 - will be the last chance for tackling it, if it is not to run out of control. As his record on world poverty shows, he is tenacious and imaginative when he becomes committed to a cause. Besides, David Cameron is piling on the pressure over global warming. If he continues to do so, we can expect more tax increases on gas-guzzlers and other measures to rein in the pollution. That mouse may yet roar.