If the plans were to become party policy, it would mean only hybrid, electric or hydrogen fuel cell vehicles, and possibly a few of the most efficient petrol or diesel models, would be permitted on UK roads. Freight vehicles would be exempt from the policy.

The deadline could also be brought forward, should technological progress allow, and the plans are said to be in aid of supporting a target of a zero-emission UK economy by 2050, and the ongoing development of a domestic low-carbon vehicle industry. The current threshold for ultra-low carbon vehicles is 75g/km CO2.

In its policy document, the party said: ‘Given that the average lifetime of a car in the UK is 13.5 years, such a change will take significant time. Motorists, the automotive industry, and the scientists and researchers investigating low carbon transport all need as much long term certainty as possible as to the direction of government policy.’

Proposals put forward also escalated VED for the least efficient vehicles, with in-service testing of a sample of cars, as conducted in some jurisdictions in the United States, to avoid any chance of manufacturers manipulating homologated fuel efficiency figures. 

According to SMMT data, alternative fuel vehicles including hybrid, plug-in hybrid and pure electric models, accounted for 2,432 of the 162,228 UK sales in the first seven months of 2013. Of these, 1,885 are plug-in hybrids or electric vehicles, which qualify as ultra-low carbon vehicles.