Post offices are suffering "death by a thousand cuts" because of plans to axe card accounts, MPs have warned.
Owen Paterson (Con North Shropshire) said the 14,400 post offices operating could be cut to as few as 4,000.
And rural constituencies such as his will be particularly hard hit, he warned.
The Government is to axe Post Office Card Accounts, which are used to collect payments, by 2010. Ministers want the money to be paid into bank accounts instead.
Speaking in a Commons debate, Mr Paterson said: "The post office has a serious social function, because those who visit it often live alone and may be elderly.
"If they do not turn up for their payment or their pint of milk, that will be brought to people's attention.
"That has an incalculable social benefit that none of us can put a finger on, but which is very tangible."
He added: "According to the National Federation of SubPostmasters, there are 7,854 rural post offices and 12 million customers a week. "Who will get a grip on the problem, and who will come up with a coherent, clear strategy for the 14,400 post offices?"
Trade and Industry Minister Jim Fitzpatrick said: "Advances in technology, greater mobility and changes in shopping and financial habits have resulted in a growing proportion of people simply not using post offices as they did in the past. Custom across the network has sharply reduced, creating the spiral of decline."