Up to half of households in a town in Cornwall are not getting daily postal deliveries, local councillors claim.
Liberal Democrats Alex Folkes and Sasha Gillard-Loft said they been told people in Launceston, which has a population of 7,000, only had deliveries about every three days.
They claimed the problem was because of short-staffing at the town's delivery office.
Royal Mail said it would investigate the situation.
Mr Folkes said he knew local Royal Mail staff were "a very friendly and hard-working bunch".
He added: "But it's a big problem if there are too few of them, and it seems that they are so short staffed that even doing a bit of overtime can't solve the problem."
Royal Mail said it was "concerned to hear about problems with mail deliveries in the Launceston area, as every letter is important to us".
It added: "We will be investigating the concerns of customers and we would urge anyone with issues about their deliveries to contact customer services, so that we can track and investigate immediately."