Royal Mail bosses are under pressure to avert a Christmas meltdown after photos appeared to reveal a huge backlog of items from a wave of strikes.
Images said to have been taken in the last few days show mountains of packed mail bags and cages piling up at depots in North West England, South West London and Essex.
The latest 48-hour strike by members of the Communication Workers Union ends on Thursday, at the start of the busy festive period.