The RAC has revealed that the poorest 10% of car-owning households in the UK are spending more than a quarter of their disposable income on buying and running a vehicle.
The research uncovered that of the £167 poorer households spend each week, £44 goes on car-related expenses.
By contrast, the richest car-owning households spend 12% of their income on buying and running a vehicle.
The research is based on "previously unreleased" data from the Office for National Statistics, the RAC said and it showed that of the £44 weekly car expenses, £16 goes on fuel and £8.30 on insurance, with £4.80 going on repairs and servicing.
"These figures should shock the chancellor," said Professor Stephen Glaister, director of the RAC Foundation.
"We already knew transport was the single biggest area of household expenditure bar none. But this spending breakdown just for car-owning households is not normally available.
"It lays bare the truth about the extent of transport poverty in the UK."
Industry experts are now calling on the government to reduce fuel duty, which is just one of the contributing factors to the spiralling cost of fuelling a car.
"To make any meaningful difference to those on the lowest incomes the rate will need to be cut much further."
The RAC isn't the only body to call for a cut in fuel duty; the AA has also been campaigning for motorists after it saw fuel prices rocket over the past few months.
There has been widespread concern about the rise of fuel poverty in the UK, which is defined as those spending more than 10% of income of home heating. This research suggests transport poverty is a more pressing problem for the poorest households.