Royal Mail could cut up to 10,000 jobs over the next year, according its to parent company International Distributions Services.
The delivery giant blamed the proposed cuts on the "impact of industrial action, delays in delivering agreed productivity improvements and lower parcel volumes".
Royal Mail confirmed the news this morning as it warned it expects to record a £350m operating loss for the year.
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The company said it plans to cut 5,000 full-time equivalent roles roles by March and around 10,000 by August as part of short-term cost efficiencies.
The 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."
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