Brittany Ferries is to take over routes being closed down by P&O at Portsmouth.
When P&O announced plans to close four of its 13 routes, Brittany Ferries said it would take over two P&O ships and run a service to Le Havre.
The French company now says it is also going to take over the Cherbourg route when P&O pulls out in January.
It means that although there will still be about 500 job losses at Portsmouth, passengers will have the same range of routes to choose from next year.
It is hoped that about 350 jobs may be transferred to Brittany Ferries.
Last year P&O carried 750,000 passengers on the Portsmouth-Cherbourg route.
But the company has been losing business in the face of rising competition from no-frills airlines and Eurotunnel.