The company confirmed last week’s fire on the ship in the Gulf of Mexico was caused by a fuel leak from a generator. Passengers went without electricity, working toilets and air conditioning for five days.

Agents said the widespread negative publicity generated could make cruises more difficult to sell.

The incident happened on the same day five crew died during a safety drill on board Thomson Majesty and just over a year after the Costa Concordia tragedy.

Andrew Earle, of Andrew Earle’s World of Travel in Hull, had one first-time cruise customer due to go on one of the cancelled Triumph departures next month.

He has now switched the booking to a four-night New Orleans land tour and believes the customer may never consider cruising again.

“Getting more new-to-cruise customers into the market will be that much more difficult. We have had a lot of families telling us the kids don’t fancy it,” he said.

Andy Tomlinson, managing director of Sutton Travel in Sutton Coldfield, said a couple who were considering a cruise had sought his reassurance in the wake of the Thomson tragedy.

He said: “For customers who are faltering a bit and planning their first cruise you have to emphasise how many sailings there are and how many go off without problem; it’s just getting that message out.”

Robert Broad Travel director Oliver Broad said: “It’s a chance for us to show our expertise because clients are asking more questions.”

Miles Morgan, managing director of Miles Morgan Travel, said most customers understood the nature of the Carnival Triumph incident, adding: “This needs to be put into context.”

Meanwhile, UK and Ireland managing director of Carnival Cruise Lines Adolfo Perez has written to agents to thank them for their support and to apologise for the conditions onboard the ship.

“All of us at Carnival deeply regret the hardship our guests had to face during their days on board the ship,” said Perez. “Our number one concern was to ensure the safety and welfare of our guests and crew and to get them home as soon as possible.

“Our shipboard and shore side teams worked tirelessly to take care of them and minimise their discomfort and inconvenience. We also focused on making sure their loved ones had a direct link to our Family Support Centre where they could obtain round the clock information on their family and friends on board.”

Perez continued: “Now that all the guests are safely home, our efforts are firmly focused on the ongoing investigation into the root cause of the fire and what measures we can take to ensure this does not happen again.

“These efforts are taking place in collaboration with the US Coast Guard and other independent parties. We know, however, that preliminary investigations indicate the cause of the fire was the result of a leak in the fuel return line for the number six diesel generator.”

He reassured agents that “all our ships are safe and secure”, and that all of them meet, and in many areas exceed, all regulatory standards.

“I promise we will continue to investigate in order to understand what took place and to learn what steps we can take to improve going forward,” said Perez.

“We know that holidaymakers can choose from a vast variety of options, and that they – and you – expect a fantastic cruise holiday from us. We are very sorry that this time we did not deliver.”

He added: “I really value your support for Carnival Cruise Lines, and in encouraging British holidaymakers to select a cruise on our ships. We hope you will continue to do so in the future, and we will endeavour to do everything we can to make our experiences as memorable and fun as possible for your customers.”