Millions of people in England are at risk of being cut off due to the cost of fuel and the lack of transport alternatives, a charity has said.
Transport group Sustrans' report, Locked Out, said the worst affected areas were the East of England, Cumbria, North Yorkshire and Devon.
It has called on the government to invest more in transport alternatives.
The Department for Transport said it has been investing in local transport schemes.
Transport Minister Norman Baker said: "I recognise the importance of good local transport networks in helping people to access work, training and essential services no matter where they live.
"The government's Local Sustainable Transport Fund has delivered £600m nationally for innovative local transport schemes which help to boost growth and cut carbon by creating - this includes several successful schemes in the Yorkshire and Humber region.
"In addition, we have invested £20m in developing the provision of community transport, which provides a lifeline to people across the country, as well as supporting the Wheels to Work scheme.
'Source of debt'
"On the railways, we are focused on improving operational efficiency which will help end the era of inflation-busting fare rises.
"Good rail infrastructure is essential to economic growth and fares have an important role in helping us fund the biggest upgrade to the network since the 19th Century."
The report's results are based on three indicators of transport poverty.
These included low-income areas where running a car would place a significant strain on household budgets and areas where residents lived further than a mile (1.6km) from the nearest public transport.
Areas where it would take longer than an hour to access essential goods and services by walking, cycling or using public transport were also taken into consideration.
The report, which rated communities as facing a low, medium or high risk of transport poverty, criticised the "absence of practical alternatives" to car ownership.
"Inadequate and expensive public transport and hostile walking and cycling environments are forcing millions of people to choose between debt and social exclusion," it said.
Malcolm Shepherd, chief executive of Sustrans, said: "For many people, owning a car is a source of debt and poverty, and this is unlikely to change in the long term with fuel prices going up and up.
"For decades ministers have made decisions based on everyone having easy access to a car, forcing many of us into car ownership we can barely afford and leaving others stranded.
"We need a transport system that works for everyone, not one designed to best suit those who can afford a car."
According to DfT data, a quarter of households in England do not have access to a car.
For those that do, the group said with wholesale fuel costs set to rise "more people will be trapped without urgent action and a long-term plan".
Sylvia Brown, chief executive of Action with Communities in Rural England (ACRE), said: "Increasingly the whole concept of public transport being viable in rural areas is in doubt. Buses running with one person on board are never going to be viable."
She suggested the government consider giving more financial backing to "community-led solutions" including car and taxi-share schemes, which she said might be "the way forward" in poorly-served parts of the country.