Craig Simmons, technical director of sustainability consultants Best Foot Forward, said: "It was touted as a green budget, but there were a lot of promises and very little delivery. The fuel duty rises were delayed, which means that people planning to buy a low-carbon vehicle don't know whether petrol prices will increase, so it's difficult to plan."

He said the Vehicle Excise Duty changes would have little impact.

"There are some good ideas, but nothing tangible or significant," he said.

"There is inconsistency, in that other Budget measures will have an impact on the environment, such as airport expansion and the commitment to ease road congestion.

"And those are firm commitments, while the road pricing is on a trial basis."

Mr Simmons said the way to tackle fuel poverty was not to reduce energy costs because people then had no incentive to improve fuel efficiency.

"It sends out the wrong message. The money would go straight into people's pockets, rather than towards cheaper fuel," he said.