Thousands of households across Britain will not receive their post until after 5pm under a major shake-up proposed by Royal Mail.
The postal service wants to push back deliveries until later in the day as part of plans to deliver parcels more quickly.
With many online shopping orders now made late at night, bosses want postmen and women to set off on their rounds later to give time for “next day” packages to arrive at sorting offices.
But modelling of the changes has found this could mean more than 100 areas of Britain get their post at 5pm or later, the Telegraph can reveal.
Of these, 17 areas may not get their post until 6pm at the earliest, including parts of London, Cornwall, Cumbria, Wales and Scotland.
These include Abbey Wood, New Cross, Rotherhithe and Southwark in London, as well as Truro in Cornwall, Barrow-in-Furness in Cumbria and Arbroath. Those in Kinross, near Perth, may not be handed parcels until 7.30pm.
A Royal Mail spokesman on Friday said the figures were based on “high level” assumptions and no final decisions had been taken.
She added that all letters would be delivered by 5pm at the latest, compared to 4pm now.
They are also subject to negotiations with the Communication Workers’ Union (CWU), which represents more than 100,000 postal workers and is threatening nationwide strikes in the coming weeks.
An overwhelming majority of CWU members voted for industrial action a fortnight ago following a row with the company over pay and conditions.
The union claimed the changes to delivery schedules were “outrageous”.
A spokesman said: “The changes would see our members delivering up to five hours in the height of summer heat and in the darkness of winter.
“This is just one example of how Royal Mail are running down the postal service in the UK and why our members are balloting for strike action to defend it.
“Postal workers need and deserve the support of the public to win this battle.”
Royal Mail has given postal workers a 2pc pay increase backdated to 1 April already and is offering the CWU a 3.5pc rise which depends on improvements in productivity and changes to postal worker rosters.
However, the union has dismissed the offer of pay as a “serious real-terms wage cut” when compared to soaring levels of inflation, which is expected to peak at more than 13pc in October.