Pensioners risk having their "lifeline" cut unless the government reaches a decision on the future of the 8,000 rural post officers in Britain, Age Concern has warned.
A report by the charity notes the 144 rural post offices that Royal Mail was forced to shut last year, and warns more are likely to be closed as 90 per cent run at a loss.
Calling on the government to renew the post office network's £150 million-a-year subsidy - which expires at the end of March 2008 - it highlights the integral part rural post offices play in the community.
Age Concern's director general Gordon Lishman said: "The message from older people couldn't be clearer. Rural post offices play a vital role in the community which stretches far beyond providing a postal service.
"The government must stop dragging its heels on the future of rural post offices. If it fails to renew the subsidy, thousands of post offices could be forced to close down and thousands more vulnerable older people could be cut off from their local community."
He stressed that the government must "consider social as well as commercial factors when making its decision".
The survey finds that nine out of ten over 60s rely on their local post office services - with 99 per cent considering it a "lifeline" - and over half (56 per cent) saying they would feel financially and socially isolated" if their branch closed.
Three-quarters said their main worry was losing access to essential services if their post office was forced to close, with the same amount worried they had no suitable alternatives.
Elderly people called the post office "the centre of our village activity", saying it "acts as a networking centre", and can help lonely people beat depression.
The report urges the government to approach the issue imaginatively and "develop a positive, coherent and sustainable rural strategy".
"Only by committing to a continuation of the rural subsidy and ensuring that essential services can be accessed locally will the government ease the anxiety of thousands of older people in rural areas," it says.
A spokesman for the Department of Trade and Industry (DTI) insisted it "recognises the wider role that the Post Office plays, which goes beyond just the commercial provision of postal services".
Noting that £750 million had been given to the rural network as part of an "unprecedented investment.of more than £2 billion to help maintain the network", he added that the DTI wanted to create "a viable post office network that meets the changing needs of customers and local communities".
Royal Mail urged the government to reach a decision soon, with a spokesman saying it "must decide what size and shape of the post office network it wants and to be clear about how that network will be funded".
A government sub-committee - chaired by deputy prime minister John Prescott - was developed to discuss the post office network. The main problem is the conflict between the commercial pressure to make a profit, and the risk of excluding certain sections of the community if further closures go ahead.