Royal Mail will consult on up to 6,000 redundancies as the delivery giant blamed industrial action for mammoth financial losses.
The firm said the move is in response to the “impact of industrial action, delays in delivering agreed productivity improvements and lower parcel volumes”.
It said it is seeking short-term cost efficiencies through the planned reduction of 5,000 full-time equivalent roles by March and around 10,000 by August.
This is expected to require between 5,000-6,000 redundancies by August.
Royal Mail is expected to fall to a £350 million operating loss for the year after being hit by industrial action, its parent group International Distributions Services said.
The cuts announcement comes a day after Royal Mail workers in the Communication Workers Union (CWU) launched a fresh strike in a long-running dispute over pay and conditions.
Royal Mail chief executive Simon Thompson said: “This is a very sad day. I regret that we are announcing these job losses.
“We will do all we can to avoid compulsory redundancies and support everyone affected.
“We have announced today losses of £219 million in the first half of the year. Each strike day weakens our financial situation.
“The CWU’s decision to choose damaging strike action over resolution regrettably increases the risk of further headcount reductions.”