Around 1,100 workers at P&O Ferries are to be made redundant as part of a plan to make the business "viable and sustainable", the company said.
The proposal involves more than a quarter of the workforce losing their jobs.
A spokesman for P&O Ferries said: "Since the beginning of the crisis, P&O Ferries has been working with its stakeholders to address the impact of the loss of the passenger business.
"It is now clear that right-sizing the business is necessary to create a viable and sustainable P&O Ferries to get through Covid-19.
"Regrettably, therefore, due to the reduced number of vessels we are operating and the ongoing downturn in business, we are beginning consultation proceedings with a proposal to make around 1,100 of our colleagues redundant."
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