Berlitz has revealed that cruise expert Douglas Ward will warn travellers of a number of "rip-offs" in the 2011 Complete Guide to Cruising and Cruise Ships.

The travel guide publisher pointed out that cruise operators have a number of ways of getting more money out of their passengers.

Among the revenue-raising techniques highlighted in the new guide is the extra gratuity, which cruise lines often place on receipts for things such as spa treatments or drinks, despite 15 per cent already having been added to the price.

Cruisers are also urged to be aware of the rising cost of products such as bottled mineral water for shore excursions and bingo cards, while many companies charge high prices for tours of the bridge and other off-limits areas of the ship.

Mr Ward provides a number of money-saving tips in the soon-to-be published guide, including travelling at off-season times, opting for an interior cabin and sailing on a ship that was built before 1980.