Almost 15 million people were left waiting for post over the Christmas period, with half reporting they went at least a week without any mail.

According to Citizens Advice, which is the consumer advocate for the postal sector, 2.5 million people missed receiving their post, with some facing penalties as they failed to pay bills.

Its research found 3% said they couldn’t pay a bill, 8% said they missed an important document and 7% said they missed a health appointment. For 4%, they were left out of pocket as a result of the delays.

The charity said not only did people face delays over Christmas, but 23% said they faced disruption in mid-January. Over half of those polled (54%) said they hadn’t received any post for over a week.

Those living in London (35%), the South East (32%) and the North West (31%) were most likely to experience a letter delay. But Chelmsford, Willesden and Upminster residents faced eight weeks of disruption.

Citizens Advice noted this is the second year running that Royal Mail has experienced problems in delivering post. Last year, 16.5 million were affected.

As such, it is calling on the communication regulator, Ofcom, to investigate Royal Mail’s performance, and consider enforcement action and fines.

“The regulator and Royal Mail must learn lessons from the disruption of the past two years to prevent this from happening again”, it said.

Clare Moriarty, chief executive of Citizens Advice, added: “A staggering 2.5 million of us missed important documents, health appointments, or were unable to pay a fine or bills due to post delays over Christmas.

“We understand the strain the pandemic has placed on Royal Mail. But after two years of disruption, Royal Mail cannot let poor service become the new normal. These delays can have serious consequences for those left waiting for their letters.

“Ofcom must now investigate Royal Mail’s performance and consider enforcement action and fines to ensure lessons are learnt.”