Labour has been warned against cutting the Post Office network due to fears over the impact on pensioners. The Government is carrying out a consultation on whether to ditch the rule to keep at least 11,500 branches open.
But Dennis Reed, director of the Silver Voices campaign group for over 60s, insisted that Post Offices are a "sanctuary" for older people who have been left behind in an increasingly digital world. He added that it "keeps the cash economy alive" amid concerns of a move towards a cashless society.
Writing in the Daily Express, Mr Reed said: "Labour would be bonkers to consider slashing the local Post Office network, or leaving the network's fate in the hands of the market.
"It is difficult to overestimate the importance of the local Post Office to millions of older people.
"The Post Office is a sanctuary for all those who are digitally excluded from many other services and the Post Office keeps the cash economy alive.
"Older people can access their pensions and benefits, pay bills over the counter and post presents and cards."
The Daily Express is campaigning against cuts with our Save Our Post Offices crusade.
Mr Reed added: "Older knees will be trembling at the thought of losing essential local Post Offices and congratulations to the Express for launching this campaign.
"The local Post Office is the last bastion against the march of the digital world, which is leaving millions of pensioners behind.
"You can still get your pension paid in cash at the Post Office, you can pay your utility bills by cheque or cash, you can pay in cheques and do simple banking in the growing absence of local bank branches. And of course buy stamps and post letters and parcels.
"The Government should not be entertaining any reduction in Post Office branches, which provide an increasingly essential public service.
"Labour is obsessed with all things online and seems prepared to jettison this vital and efficient network which supports the cash economy and provides a vital human link with public administration."
The Labour Government has said its preference is to keep the minimum branch requirement of at least 11,500 Post Offices in place.
But it is exploring other options including scrapping the limit and leaving the size of the network up to the Post Office.
However, the company would still need to ensure that at least 99% of the population stay within three miles of a branch.
The Government admitted that this "would likely be a concern to communities", adding that it is not its preferred choice.
Another option being looked at is to develop new requirements aimed at targeting local areas with insufficient service provision.
It comes as the number of Post Offices - which provide services including sending letters and parcels, banking and bill payments - has been in decline.
There were 11,805 Post Office outlets in the UK as of March last year, down from 18,393 in the year 2000.
The decline started in the 1980s and 1990s before accelerating in the mid-200s.
The Conservative-led coalition government introduced the 11,500 minimum service requirement in 2010.
Tory MP Dame Harriett Baldwin has set up a petition called Save Your Post Office, which she said has racked up more than 100,000 signatures.
A Department for Business and Trade spokesperson said: "We recognise a strong and accessible Post Office network is crucial to delivering services valued by communities across the UK.
"It is right to consider a range of options to secure the organisation's long-term future, but have been clear that our preference is to keep the overall size and shape of the network the same."
Labour would be bonkers to consider slashing the local Post Office network, or leaving the network's fate in the hands of the market.
According to the Post Office, two-thirds of Britons have a Post Office within a 10-minute journey, and four out of 10 of those, within a 10-minute walk. It is vital that this level of accessibility is maintained.
It is difficult to overestimate the importance of the local Post Office to millions of older people.
The Post Office is a sanctuary for all those who are digitally excluded from many other services and the Post Office keeps the cash economy alive.
Older people can access their pensions and benefits, pay bills over the counter and post presents and cards.
The Government would also be undermining its own plans for growth if it supports such a proposal.
Post Office research reveals that the presence of a Post Office in a local shopping centre generates 400 million visitors a year to nearby shops, pubs and other businesses.
Having already seen bank branches close, many High Streets would become desolate places without a thriving Post Office.
Many small businesses also rely on the PO for basic banking functions, and the shops in which Post Office counters are often located would struggle to survive on their own.
At a time when digital-only transactions are weakening human communications and the coherence of communities, Post Offices are a safe place where people can still talk to strangers and share gossip about the local community.
And crucially it is an official Government outpost where important face to face transactions can take place such as renewing passports and driving licences.
The support shown for the postmasters and postmistresses affected by the Horizon IT scandal represents the love and affection the public has for our local Post Offices.
It would be betraying all those campaigning heroes if the local PO network was now decimated. We must not allow this crass proposal to proceed.