Under the opposition party's proposals point of sale material would feature prominent cigarette packet-style fuel consumption and emission figure displays.

The opposition party's Quality of Life report, authored by ex-Tory environment minister John Gummer and Conservative candidate and green issues campaigner Zak Goldsmith, proposes a raft of tax initiatives it claims would cut carbon emissions from cars.

“Too often this information is poorly visible or absent altogether. The point of sale is the one moment when customers seriously consider fuel efficiency,” said the report. “The UK government should take an international lead in developing a code of practice - more prominence should be given to fuel economy in advertising and at the point of sale.” The report recommends a hefty purchase tax hike for vehicles with high CO2 emissions, graded up to 10 per cent of RRP, and variable VAT charges of 5 to 17.5 per cent, favouring low emission models.

“An emissions-related tax directly at the point of purchase would increase the price differential between clean and polluting new cars more steeply,” it said. It suggested that road tax hikes were poor at shifting buyers to cleaner models, and called for lower overall VED rates, particularly for the cleanest cars. It claimed this would slow depreciation of the cleanest models. However, for the highest CO2 emitters it called for a still-higher ‘H' VED band. The report also envisaged the reinstatement of ‘modest' capital grants to buy low-carbon new cars, and a mandatory, rolling extension of the EU's exhaust emission requirements, with CO2 targets of 80 to 100g by 2020.