On the day the prime minister demanded that Britain should ‘lead the world in the transformation to a low carbon economy’, one of his junior ministers admitted the Treasury was working against reducing emissions.

Only hours after Gordon Brown’s speech to his party conference in Manchester, transport minister, Tom Harris, addressed a fringe meeting organised by the All Party Parliamentary Light Rail Group.

And he disclosed that the Treasury, when assessing the business case for new tram systems, considers it a disadvantage that they persuaded people out of their cars.

‘The Treasury sees that as a net loss because of the effect of car tax and fuel duty,’ he said. ‘When you have a business model which sees modal shift as a negative, in my view, that needs some work.’