The Liberal Democrats have been voted the greenest of the three main political parties in an audit by Britain's environmental groups. The Liberal Democrats, regarded as the party with the most long-standing commitment to the environment, come out on top despite efforts by the two biggest parties to catch up. But today's report is bad news for David Cameron, who has made the environment a symbol of his attempt to change the image of the Conservative Party. Despite his efforts, the Tories are rated behind the two other parties. The report scored the parties on a traffic light system. Results: Liberal Democrat 3 Green, Labour 1 Green, Conservative 0 Green.