Around 450 job cuts are planned by the operator of British cruise lines P&O Cruises and Cunard, the PA news agency understands.
This represents more than a quarter of the workforce at Southampton-based Carnival UK.
P&O Cruises and Cunard announced last month that their sailings are suspended until at least the end of July due to the coronavirus pandemic.
A Carnival UK spokesman confirmed it has begun consulting staff across all levels of the business.
He went on: “These changes, whilst very difficult, are to ensure the future sustainability of our business.
“The Covid-19 pandemic has not only affected the holidays of our guests but it has also impacted every part of our business: our future deployment, the guest experience, our supply chain and our people on ship and on shore.
“During our pause in operations we have tried to create as much certainty and stability as possible for our staff in Southampton and crew on board our ships.
“Unfortunately though, and like many businesses, as Covid-19 has continued to impact our way of life, it is necessary to make changes to our organisation to build a stable platform for the time we phase our ships back into service and for future growth.”