Social distancing measures requiring cruise ships to operate below full capacity would be an extra hindrance to an already financially shattered sector.

Norwegian Cruise Line and Royal Caribbean pointed to protocols they fear would further hit industry’s bottom line following the shutdown of global operations since March due to the Covid-19 pandemic, according to the Financial Times.

The US Centers for Disease Control and Prevention (CDC) has imposed deep restrictions in US territorial waters.

Ships with more than 250 passengers have been banned from sailing from the US until July 24.

The EU’s interim guidance for resuming operations published on June 30 said: “Cruise ship operators should reduce the number of passengers and crew on board to ensure that measures related to physical distancing on board ships can be maintained, and that temporary isolation and quarantine of passengers and crew can take place individually in cabins.”

The guidelines recommended cruise companies cut the duration of voyages to between three and seven days, make fewer port calls, avoid offering buffets and get passengers to maintain 5ft of social distancing.

The guidance also urged stricter health checks for people over the age of 65, who account for 30% of all cruise passengers.

Onboard shows and activities could also be spread out by age group.

The UK Foreign Office compounded the situation on Thursday by advising against all cruise travel, acting on advice from Public Health England.

Norwegian and Royal Caribbean have assembled a panel of experts to develop health protocols that are expected by the end of August.

Carnival Corporation has also assembled its own group of experts to take part in a summit on the impact of coronavirus.

Norwegian and Royal Caribbean have said cruises would not resume until the new protections are fully in place.

Norwegian Cruise Line Holdings chief executive Frank Del Rio told the FT: “One of the hallmarks of the cruise industry is that we always sail with full ships. It’s one of the basic tenets of our business model.”

Royal Caribbean Cruises chief executive Richard Fain said: “There isn’t a one size fits all answer to this.

“There are different steps that are appropriate at different times and different places.

“A lot of people assume that you simply take what happens on land and apply it on to the sea.”