The cliff-edge date is a key part of the Government’s Net Zero move.
But the switchover to electric vehicles would cost around £400billion, dwarfing the environmental benefits of £76billion, analysis by the Centre for Economics and Business Research shows.
Most costs will be faced by business initially but others will hit families in lower profits and wages and higher taxation up until 2050, it claims.
FairFuelUK founder Howard Cox said: “Our 1.7million supporters call on Liz Truss to end the virtue-signalling attempt to ban new diesel and petrol cars.”
The study says the biggest cost is buying new electric vehicles, which will be £188billion dearer than their petrol equivalents in total.
The value of the extra time drivers will spend waiting for charging electric vehicles rather than pumping in fuel is calculated at £47billion.
Meanwhile public investment needed for charging points and electricity-generation infrastructure is put at £99billion.
Findings for the Fair Fuel All-Party Parliamentary group also show a likely average loss in tax revenue of £2.7billion per year as fuel duty and VAT on petrol and diesel fall away.
But environmental benefits are lower than expected due to increased emissions from electric vehicle production, it says.