Although it is not clear exactly what prompted the industrial action, it is believed staff are unhappy with recent managerial decisions and staffing levels within the office.

The walkout is understood to have delayed mail delivery times by around an hour.

A spokesman for Royal Mail said, “Some members of staff in the Dundee East delivery office did take brief unofficial industrial action this morning.

“All staff are back at work, and measures are in place to ensure this has no impact on the service to customers.

“Royal Mail management are engaged in talks with union representatives to resolve any issues and prevent further damaging and unnecessary industrial action.”

The sorting office has a long history of industrial action. Earlier this year, Royal Mail managers from across Scotland had to be drafted in to help clear backlogged mail caused by staff walkouts.