Royal Mail has proposed reducing delivery of second-class letters to every other weekday, as part of its efforts to cut costs.
The suggestion was included in a proposal to Ofcom which the struggling company said would save it £300m.
Under the universal service obligation (USO), Royal Mail is legally required to deliver letters six days a week and parcels from Monday to Friday, but the number of letters being sent has dropped significantly and Royal Mail says the current system is "not sustainable" and reforms are "urgently needed".
The company's service levels have also deteriorated with many customers complaining that deliveries, including important medical and legal documents, regularly don't arrive on time. Ofcom fined Royal Mail £5.6m last year for its poor performance.
In its proposal, Royal Mail also said the delivery speed of standard bulk business mail, used by large mail shippers for bulk mailings such as bills and statements, should be aligned to second-class, so they arrive within three weekdays instead of two currently.
Ofcom previously proposed Royal Mail dropping Saturday deliveries, but the company did not include that saying it