The group said recent trends have affected how much post people receive.
The Royal Mail says UK households may not get post for several days. The group said recent trends have affected how much post people receive.
A Royal Mail spokesman said: "We understand how frustrating it can be when letters are delayed. We want to reassure customers that the vast majority of First Class mail arrives the next working day."
The company said that where First Class items are delayed, 92 per cent will arrive within two days, while 99 per cent of items will be delivered within five days. However, the postal service also cautioned that customers may experience several days without any deliveries.
The spokesman said: "As the volume of letters has fallen dramatically over the past decade, it is now increasingly common to go several days without receiving any post if nothing is expected. However, if you have concerns about missing mail, please get in touch and we will investigate."
But online, one household fumed: "Proper cloak and dagger language there from RM. Absolute shysters. Despicable lies."
"They are sitting in the walk sequence machines until they are released on 5th day, just like last Thursday," another typed.
Another fumed: "Yep royal mail still lying to the customers. It's being held like it has done for years. Then it is often sitting in a tray or frame until it finally gets delivered. Then the customer gets 9 letters all at once.
"This isn't a volume dropping thing. It's a cost cutting, service f***ing, royal mail thing." Another said: "There isn't very much 1C mech atm so the 2C just builds up and builds up until a load hits the 5 day limit, like last night."
"Thought everything was gonna change with the new owners it's exactly the same," another commented on an online forum.
"Then stuck in a frame at least every other day," another said.
