Holidaymakers opting for a cruise must ensure they are covered by their travel insurance policy before setting off, a leading insurer warns.

Many policies have an upper cancellation claim limit of £5,000 but the cost of cruises often exceeds this, according to American Express.

Most also impose restrictions on the number of days per trip that can be spent outside of the UK yet holidaymakers need to be insured for the duration of their time abroad – and the countries and ports they may stop off in.

In addition to this, the extra costs involved in dealing with medical emergencies at sea mean that many insurers do not cover cruises.

American Express also estimates that the cost of calling out an air ambulance on the eastern coast of the US can exceed £30,000, even before receiving medical treatment on dry land.

Joanne Field, of American Express Insurance Services, said: "Travel insurance is just as important on a cruise as for any other type of holiday. Clearly it is reassuring to know that there are trained medics on board but that does not make travel insurance any less essential.

"When people are taken ill at sea and need urgent treatment, transportation from the cruise ship to the nearest hospital can be an added complication sometimes involving the use of an air ambulance. Without insurance, the cost of this alone is likely to run well into four if not five figures."