Postal workers at a Royal Mail depot in Bristol held a meeting this morning, and will be sent ballot papers to decide if they will go on strike.
Workers at the Mead Street office in Bedminster say they've ended up with a backlog of deliveries.
Royal Mail blamed high levels of sickness for the backlog.
David Wilshire from the Communication Workers Union (CWU) says the Christmas post could be affected:
More top news
We've been getting acquainted with the Shaun the Sheep sculptures heading out on location for this summer's trail across Bristol
The Shaun in the City sculpture trail, which hits Bristol's streets on Monday, was given its official, and typically unusual, launch today.
Not enough beds and an agonising wait for the right help - a mother describes the anguish of trying to save her anorexic daughter.