Almost three in four English councils are reviewing or making cuts to school transport, according to newly released figures.
The data relates to 81 English local education authorities outside London and the six big metropolitan areas in England. It was obtained following a Freedom of Information request by the Campaign for Better Transport (CBT).
The CBT said 38% of councils were reviewing or cutting transport to faith schools; 46% were reviewing or cutting transport to schools other than faith schools and 51% were reviewing or cutting post-16 transport.
In total, 72% were reviewing or cutting one or more areas of school transport.
The CBT said councils are obliged to provide free school transport for pupils between five and 16 years old if their nearest school is more than three miles away, or two miles if they are under eight.
There are also provisions for children with special educational needs, and for some children from low income families. However school transport provision over and above this is provided by local authorities on a discretionary basis.
CBT bus campaigner Sophie Allen said: "School buses are vital to reduce congestion and pollution, especially at peak times. In some areas parents could have to walk almost three miles each way, twice a day, just to get their children to school.
"Parents able to drive instead will add to traffic problems, but for quarter of households who do not have a car this will not be an option."
The CBT said it was calling on the Government to give councils extra funding to ensure that children can get to school safely and working parents are not unfairly forced to give up work.
Shadow transport secretary Maria Eagle said: "These shocking new figures show just how out of touch ministers are with the impact their cuts to local buses are having. The scale of cuts to local bus services has left many parents struggling to afford the extra costs of driving their children to school or to juggle work with doing the school run."