Lib Dem plan to drive all petrol and diesel cars off the road by 2040 to force motorists to go green Nick Clegg's party wants everyone to drive low carbon cars within 30 years Only freight lorries would be allowed to create high levels of pollution Plan will become Lib Dem policy at annual conference next month Petrol and diesel cars would be banned entirely from Britain's roads by 2040 under Liberal Democrat plans to force everyone to go green Nick Clegg's party has unveiled proposals to only allow ultra-low carbon vehicles, such as electric cars and hybrids, by that year. However, although ordinary petrol and diesel cars would be banned, such vehicles would still be allowed for freight purposes. Thing of the past: Lib Dems want only ultra-green low emissions cars on the roads within 30 years The move would pile further pressure on hard-pressed motorists, who are also having to cope with sky-high fuel bills. And - to attract the anger of drivers even more - the Lib Dems would also like to see councils given the power to impose road tolls to ease congestion in city centres. The plans, which have the support of the party leadership, will be voted on by delegates at next month's Lib Dem conference in Glasgow. The controversial motion will be moved by Lord Teverson, co-chair of the party's official committee on environment and climate change, and a former manager of international freight company Exel. If members vote yes, the policy will have to be included in the Lib Dem manifesto for the next election. The idea of banning ordinary cars is contained in a policy paper entitled "Transition to a Zero Carbon Britain" which will be debated in Glasgow. It states: "By 2040, only ultra-low carbon vehicles will be permitted on UK roads for non-freight purposes." In the years until the ban comes into force, the policy paper reveals that Lib Dems want to charge higher taxes on petrol and diesel cars to persuade motorists to move towards greener alternative. Going green: The cars clampdown is part of a raft of environmental policies being pushed by Nick Clegg's party at its annual conference next month Cleaner vehicles would attract a subsidy, paid for by a higher "vehicle emissions duty" on less environmentally friendly cars. The Lib Dems also want to introduce a system of road pricing - that is, tolls - in congested areas. While the Coalition ruled out imposing tolls on the existing road network during this side of the election, no promises have been given for the second half of the decade. The document said that party would prepare for the "introduction of a revenue-neutral system of road pricing and support local authorities introducing road pricing in congested areas. The Lib Dems also want to replace air passenger duty with a "per-plane duty, charged in proportion to the carbon emissions created by that journey." As part of the party's plans to create a "zero-carbon" Britain, the Lib Dems could also embrace nuclear power and shale gas exploration. The policy document says that gas fracking should be allowed as long as "regulations controlling pollution and protecting local environmental quality are strictly enforced, planning decisions remain with local authorities and local communities are fully consulted over extraction and fully compensated for all damage to the local landscape."