A Post Office may be reopened when a branch, currently run from a newsagents, closes in June.
Councillors in East Grinstead said it would be "absurd" for the town not to have a post office after the owner of newsagent Forbuoys announced closure of the operation.
Mid Sussex MP Nicholas Soames said losing the service was "unthinkable".
He has received a letter from Post Office Ltd confirming the closure of its London Road counters. Managers, however, insist that services will be retained with a branch reopening nearby.
Adrian Wales, of Post Office Ltd, said: "I assure you that any closure will be temporary and we are giving our urgent attention to ensuring services are maintained in the area."
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