Postal services were hit yesterday morning when the Post Office’s computer system went down.
Customers said they were unable to post parcels and were told that staff could not deal with anything which required a computer.
The problem hit branches across the country.
A Post Office spokesman said: “The Post Office apologises to its customers for the inconvenience caused by a computer problem currently affecting the service at branches across the UK.
“We are very sorry for any difficulties this has caused our customers. We are doing everything we can to fix the problem as quickly as possible and restore a full service to all branches.
“Branches are making special cash payments to Post Office Card Account customers. Post Office ATMs and Post & Go services in branch are unaffected. Bill payments and e-topups for mobile phones can be made at Paystation terminals in Post Office branches.”
Andy Burrows, of Consumer Focus, said: “We are concerned that this is the fourth major service interruption in the Post Office’s electronic systems in nine months. We will be meeting with Post Office Limited to understand how the problem will be addressed.”