Almost 200 people have been made redundant at Condor Ferries as a result of the coronavirus pandemic, the company has said.
Chief executive Paul Luxon said the cuts affected 37% of its staff, which the company said was about 500 strong.
Mr Luxon said it was a consequence of a 75% fall in income over the last five months.
He said a limited schedule between the Channel Islands, the UK and France would remain till the end of the year.
Condor said it had received no revenue from passenger services between March and early July due to the lockdown, with freight volume down 40% over the same period.
In early July, the company was forced to cancel its planned restart of services between Jersey and St Malo when baggage handlers in France went on strike.
Mr Luxon said the company had faced "the perfect storm" at "the busiest time of the year".
Condor has since been able to operate sailings to Jersey from St Malo and Poole after Jersey reopened its borders to non-essential travellers.
While the company said it had expected Guernsey to do the same in early September, that prospect is now "improbable".
In a letter to customers, Mr Luxon said "drastic changes" had been made to protect the company's future, including "a resizing of the business".
He did not confirm exactly what the "limited schedule" would look like.
"We fully recognise our responsibilities for supporting the visitor economy, travel for Channel Islanders and for bringing in essential freight, and whilst none of us can use a crystal ball to predict the future, we hope that normality can, at some point, return," he said.