Postal services watchdog Postcomm is to urge the government to end uncertainty over the future of the 14,000 Royal Mail post offices.
Fewer than one-third of 8,000 rural post offices cover costs
Postcomm says ministers need to take into account the wider social role played by post offices as they decide what to do.
Fewer than one-third of the 8,000 rural post offices cover costs, despite subsidies of more than £150m a year.
The call comes amid reports that Royal Mail wants to shed 30,000 jobs.
The UK postal market was opened up to greater competition from 1 January, and the Royal Mail has been calling for greater freedom to increase its prices and limit losses.
In 2004, it was announced more than 1,600 rural post offices could be shut down under new regulatory recommendations.
Postcomm has said the £150m-a-year subsidy, which helps sustain the rural network of post offices, is due to be withdrawn by the government in 2008.