Rural Scotland will suffer "disastrously" if a plan to close thousands of post offices is carried out, says a watchdog and politicians.
Critics say post office closures will hit rural communities
Postwatch Scotland's concerns follow speculation that Royal Mail could close up to 3,000 post offices across the UK.
The SNP's John Swinney said Scottish ministers should now speak with a clear voice and demand reassurances over the future of rural post offices.
The Liberal Democrats have also warned against the phased closures.
Royal Mail has told ministers that post offices are losing millions of pounds a week despite a recent closure programme.
The chairman of Postwatch Scotland, Dr Tom Begg, said closures in some remote communities would be "absolutely disastrous".
He called for any closures to be carefully considered.
Dr Begg added: "The worst thing to do is to just simply allow Post Office Limited to go ahead with closures on the basis of what they need for their balances.
"Post offices are too important to communities, and indeed vulnerable members of communities, to allow it to be done in that brutal way.
"We need a system in place that considers the needs, particularly I have to say, of the more rural communities."
Mr Swinney, the SNP's finance and public services spokesman, led a debate in the Scottish Parliament last week on the future of the post office network.
He has called on the executive to make its voice heard on the issue.
Mr Swinney said: "There are already signs that business is falling away from post offices since the government withdrew many vital services.
"It is absolutely vital that the Scottish Executive speaks with a clear voice and demands the government provides a secure future for rural post offices.
"Unless they do, and unless ministers at Westminster listen, the UK Government will be responsible for delivering a body blow to economic and social activity to communities in Scotland."
Gordon MP, Malcolm Bruce, also warned that potential closures would have disastrous consequences for rural Scotland.
The Liberal Democrat MP has just completed a survey of post offices in his constituency and found that many are loss-making and face an uncertain future.
He said: "£150m across the UK is a small subsidy to maintain vital services in rural communities, and would be in any case much less if the government put more business opportunities through post offices rather than taking them away as they have systematically been doing."