One of the country's most powerful unions is leading a campaign against "savage cuts" to bus services in the Westcountry.
The RMT has promised to fight plans by two major providers to axe a series of "lifeline" routes in Cornwall following proposals to scrap other services in Devon.
A number of services by Western Greyhound across the Duchy will be withdrawn, while First Group may terminate routes in Falmouth.
RMT expressed concerns that the move may lead to a "domino effect" on other services across the region.
Bob Crow, general secretary, said: "These savage cuts to services on South West buses could well open the floodgates to an all-out attack which would decimate lifeline services across whole communities as the bus companies wheel out a pack of excuses to justify cherry-picking the profitable routes."
The union also warned the savings would particularly hit older people, the poor as well as those with disabilities – and could effectively cut off entire communities.
RMT added that the plans "made a mockery" of a recent Transport Select Committee report pressing the Government to increase disabled access to transport.
Western Greyhound managing director Mark Howarth said the changes came after "extensive negotiations" between the company and council officers.
In a letter to staff, he said: "We have been notified that due to budget cuts, Cornwall Council will be withdrawing financial support for a number of services, some of which are operated by Western Greyhound."
Routes to go from November 3 include its Penzance and Hayle operation, the 530 in Bude and the 561 Camelford-Wadebridge-Bodmin service.
Mr Howarth promised "most evening and Sunday journeys will be retained" and said he hoped that Cornwall Council would find money for "partial replacements" in the form of community buses or other alternatives to replace the withdrawn bus routes.
A formal consultation has begun for affected staff and job losses are yet to be finalised, he added.
Several remote villages will be affected by the cuts, including in North Cornwall where the 530 runs to villages including Morwenstow and Kilkhampton, and on Bodmin Moor where the 561 serves St Breward and St Tudy.
Cornwall Council said it was working to protect services, with around 90% of the network currently provided by First Group and Western Greyhound.
Bert Biscoe, cabinet member for transport and waste, acknowledged that one of the proposals put forward by Western Greyhound "was to withdraw all their services from the Penwith area".
He said: "We recognise the impact this would have on local communities and have been endeavouring to work with the company to identify alternative options.
"Ultimately, however, this is a commercial decision for the bus operator."
A First Group spokesman told the Western Morning News that "big substantial changes" to its services would be announced by the end of September.
The latest changes come after it announced in July plans to stop running bus services in North Devon and close its Barnstaple depot.
Cornwall and Falmouth councillor Candy Atherton said the cuts would "trap people in their homes".
"I am appalled that First have not told the town council or ensured that people knew what was happening," she added.
Bernard O'Neil, secretary of the National Pensioners Convention in Cornwall, warned the cuts would have a "big impact" on older people living in the Duchy.
"It will have a knock-on effect all the through. If people can't go out, they will become isolated, which could lead to mental health problems affecting the NHS," he said.
Mr Crow added: "RMT will step up our campaigning work with the communities to stand up and fight these cuts."