The change, which came into force on July 10 and applies to new bookings, sees the line paying commission on the full value of a cruise in which a passenger uses a future cruise credit to pay for part or all of the sailing.

The line said its news system calculates commission based on the value of the cruise prior to the application of the future cruise credit.

Previously, Carnival calculated commission on the price of the cruise after a future cruise credit was applied.

The new arrangement applies in the US only and the line has currently made no announcement whether the scheme will be extended to international markets.

Adolfo Perez, vice-president sales and trade marketing, said: “Our team is always listening and looking for ways to offer the best sales and service support we can to travel agents and this commission enhancement is a reflection of that goal.

“We value the hard work travel agents put into booking their clients, which is why we’ve increased the commission for these types of bookings.”