Three post offices in Brighton could close to safeguard the future of other branches.
Post offices at Bates Road, Ditchling Road and Havelock Road are expected to shut in March.
George Hooper, the Post Office's area chief, said closing the three branches would improve the prospects of nearby branches.
He said a final decision had not been taken and the Post Office would consult with people who use the branches.
Rising overheads and changes to the way pensions and benefits are paid have made it difficult for competing branches to stay profitable.
From April, the Government will begin paying pensions, benefits and some tax credits directly into bank accounts.
Mr Hooper said: "Proposals to close Post Office branches are not made without considerable research and discussion.
"We are anxious that customers and all relevant organisations understand our rationale and have the opportunity to give us their views.
"We have a responsibility to ensure that customers in Brighton will continue to have reasonable access to local Post Office products and services.
"Even after any changes are made, well over 95 per cent of customers will still live within a mile of a post office branch."
The Post Office said branches at Preston Drove, London Road and Hollingbury Place would be expanded if the proposed closures went ahead.
Consultation on the closures is until February 3. Anybody who wants to comment should write to: National Consultation Team, PO Box 641, St Albans AL1 5XN.
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