"
Senior national secretary Allan Graveson said: "These ships are inherently unstable. Some have heeled over.
"Designers are going for the maximum height they can and putting on as many decks as they can because that's what the customers want and it's a way of maximising revenues."
Robert Ashdown, the European Cruise Council's technical, environment and operations director, dismissed the fears saying cruise liners are "more stable than they have ever been".
"They can stand up to anything the weather can throw at them. They are designed to strict international standards," he said."If the damage is severe, the ship should be able to stay afloat for three hours so that an orderly evacuation should take place."
Nautilus said that the sheer number of people on the huge liners, however, raised "serious questions" about the evacuation process.
"Insurers and salvors have also spoken about the way in which the sheer size and scale of such ships presents massive challenges for emergency services, evacuation, rescue, and salvage," general secretary Mark Dickinson said.
Passengers on the Costa Concordia have described the evacuation process as chaotic and experts criticised crew for not getting people to lifeboats quickly enough.
Professor Ed Galea, a safety expert at the University of Greenwich, said: "Had the evacuation process started when the ship was holed we possibly would have seen a very different picture.
"The passengers would have been assembled in 40 minutes, maybe up to 60 minutes, and then they would have been able to board the lifeboats while the ship was still upright."
William Gibbons of the Passenger Shipping Association told Sky News that "safety at sea is paramount.
"All the crew and officers are fully trained in safety procedures.
"Our track record speaks for itself. This type of incident is so rare it is almost entirely unprecedented."
But Nautilus said that investigators should examine staff competence, as well as the manning of the bridge and engine room, and lessons should be learned.
"We believe that more attention needs to be given to such issues as the adequacy of life-saving appliances, and the quality and quantity of crews and their training and experience in operating these vessels and dealing with emergency situations, including evacuation."
With thousands of people on board, many people have also raised concerns about personal safety while on cruises."
http://news.sky.com/home/world-news/article/16149985