Boris Johnson has been warned by his own economic experts that his drive to outlaw petrol and diesel in favour of electric vehicles may disproportionately help the well-off at the expense of the poor.
Sales of new vehicles with internal combustion engines will be banned in 2030 in a bid to reduce emissions to net zero by the middle of the decade.
And ministers unveiled a raft of additional measures today designed to push Brits into buying electric vehicles (EVs) at an increasing rate even before then.
Manufacturers could soon be forced to sell a rising share of electric vehicles each year to speed-up the shift.
The Department for Business Energy & Industrial Strategy confirmed it will consult next year on the introduction of a 'zero emission vehicle mandate' from 2024 - and it could fine car makers who do not move quickly enough.
However a Treasury review released at the same time questioned whether the rush to EVs was good for society.
The analysis of the PM's net zero plans said: 'Policies to support the adoption of EVs may disproportionately benefit higher income groups, and the costs of any policies that affect the remaining drivers may fall disproportionately on low-income groups; this could create a trade-off in some areas between incentivising decarbonisation and minimising distributional impacts.'
Mandate for electric cars: The Government will consult on plans to force vehicle manufacturers to sell a rising share of plug-in models each year from 2024
In response Downing Street insisted that net zero plans had to be 'fair' across society.
The Prime Minister's official spokesman said: 'Any policies we bring in will be designed to be fair across the board. I'm not going to speculate on potential future policies.'
Ministers see the zero emission vehicle mandate as the most effective way of shifting the UK to electric vehicles - while also allowing taxpayer-funded grants to be reduced.
'Our zero emissions vehicle (ZEV) mandate will guarantee greater number of zero emission vehicles on our roads, unlocking the transformation of our road transport,' the strategy paper said.
It was reported last week that Chancellor Rishi Sunak has been at loggerheads with Transport and Businesses Secretaries Grant Shapps and Kwasi Kwarteng over planned cuts to the Plug-in Car Grant.
The scheme, which has been available since 2011, was last slashed by £500 in April, down from £3,000 to £2,500. Additional rules were also put in place so that only buyers of electric vehicles up to the price of £35,000 are eligible for it.
The Treasury is said to be eager to scale down grants to focus funding towards bolstering the country's charging infrastructure as well as reduce outgoings in the wake of the pandemic.
Yet both Shapps and Kwarteng are concerned it could derail the recent growth in EV demand and send the wrong message ahead of the COP26 summit in Glasgow later this month.
A ZEV mandate - like the one introduced in California in the 1990s - is being looked at as a best solution, putting the onus on car makers to sell an increasing proportion of electric vehicles each year, for which they will receive credits.
This would - in theory - accelerate the availability of EVs across different price points, with manufacturers forced to introduce battery-powered models that are suitable for all different types of car buyers.
Failure to meet yearly-increasing sales targets could result in fines for the manufacturers and there would be a separate target introduced for the carbon emissions of their vehicle ranges.
As well as potentially forcing down the prices of traditionally expensive EVs and negate the need for government grants, MPs believe the mandate would provide a clearer indication of how many charging points will needed to ensure there is a suitable infrastructure for the rising use of plug-in cars.
This will also in turn give the Treasury a clearer picture of how rapidly it will lose revenues earned through motoring taxes on fossil
