MP have labelled the planned changes in car tax rates as "poorly explained and communicated", adding they do not go far enough.
The projected carbon savings from the introduction of new vehicle excise duty (VED) bands were "far less than they could be", according to a report from the House of Commons Environmental Audit Committee.
But the Treasury insisted the reforms had been explained clearly.
The report went on: "We are surprised that the Treasury has risked provoking such political opposition for an environmental measure which, according to its projections, is of limited benefit."
The committee was also disappointed "that the Treasury had not calculated what the impacts of the (VED) Budget (changes) will be on emissions from second-hand cars, when this was one of the main objectives of the changes."
MPs said a failure to advertise green tax details to the public "breeds suspicion about their objectives, increasing the perception of them as revenue-raising measures with no environmental purpose."
The Treasury should pay more attention to communicating the details and objectives of VED and other environmental taxes in the future, and should examine the case for a more ambitious reform of VED, the report added.
The committee looked at the whole question of VED following the announcement in this year's Budget that VED rates were to rise for existing cars with higher emissions registered since 2001.
Copyright © PA Business 2008