Postmen are being told to walk faster when delivering post to ensure they complete their rounds quicker, according to a union.
A new software system which calculates the optimum post load that can be delivered, is commanding Royal Mail workers to walk at four miles per hour.
The Communication Workers Union (CWU) says the system is being used to make financial savings without considering the realities of the rounds.
Bob Gibson, a national official at CWU, claims the new software is putting pressure on delivery workers and leading to bullying and harassment.
"CWU has an agreement with Royal Mail to jointly review all aspects of Pegasus, but the business has reneged on this and is pushing ahead with damaging changes without input from the union," he adds.
Postal workers from six sorting offices will be staging a strike on December 19th due to proposed centre closures, which is supported by the CWU.