Cuts to bus services are now reaching "critical levels", according to a report by the Campaign for Better Transport (CBT).
As many as 47% of local authorities in England and Wales have reduced their support for buses for 2013, while the 2014/15 financial year is likely to be a difficult one for bus services, said CBT.
Three councils have stopped supporting services and others might follow, warned the CBT, whose report is entitled Buses In Crisis and is based on responses to Freedom of Information Act requests made to all local transport authorities regarding supported buses.
Key findings in the report include:
:: In the last year there have been £17 million of cuts in the budget for support buses in England. Plans for cuts of £48 million have already been announced for future years, with the likelihood of more to come;
:: Counties making year-on-year cuts of more than 10% to support for buses include Shropshire, Hertfordshire, Cambridgeshire, West Berkshire, Hampshire, Surrey, West Sussex, Wiltshire, Dorset and Gloucestershire;
:: 47% of local authorities have reduced their spending on supported bus provision this year;
In addition, county counties considering cuts include Worcestershire, Cumbria, Oxfordshire, North Yorkshire, Dorset, Essex and Nottinghamshire.
Cuts could be made by Transport for London, West Midlands transport authority Centro and the Welsh Government, the report said.
CBT public transport campaigner Martin Abrams said: "Cuts to bus services are now reaching critical levels. We have seen services lost year on year and with further deep cuts planned next year, some authorities may stop supporting buses altogether.
"This is a watershed moment. If Government doesn't take action to help support buses, we will see whole networks disappear.
" Politicians, both locally and in Westminster, need to understand how important buses are.
"They may not be as politically sexy as big transport projects but they make a significant difference to the economy, the environment and to wider society. It would be a disaster if whole networks were allowed to disappear."
The report's recommendations include i ntroducing minimum access standards, having a new approach to funding, bringing in long-term investment and increasing patronage through the Government fully funding concessionary travel for the young and old.
Chairman of the Local Government Association economy and transport board Peter Box said: "Councils know how important local bus services are to their communities and have been working hard to protect them where possible.
"However, they are contending with 43% budget cuts, reductions to bus-related grants and the spiralling cost of the concessionary travel scheme which Government has never properly funded.
"Many councils simply can't afford to subsidise bus companies to operate unprofitable routes at the levels they once did.
"Where bus companies stop running services, councils will look at other ways of helping people who used them, such as supporting community transport schemes and co-ordinating with local health service fleets.
"We have long told Government the current funding system needs to be reformed so we can get the most out of our diminishing resources.
"Rather than Whitehall handing over money to bus companies with no strings attached, councils and passengers should be put in charge of commissioning services.
"Bus companies can then be made to compete for funding at a local level, with the people who use them having a greater say over which services are provided in return."
A Department for Transport spokeswoman said: "We recognise that local authorities are making difficult choices in a challenging climate. That is why despite the tough economic times we have protected bus spending as part of the last Spending Review.
"Local authorities are best placed to decide how to provide supported bus services - reflecting local needs and within available budgets."
Shadow transport secretary Mary Creagh said: "This out-of-touch Government's policies are damaging local bus services.
"Bus passenger numbers are down and routes are being cut. Bus services are crucial to supporting local communities and ensuring people can get to work, school and visit friends."