The study by the Consumers' Association, which surveyed 23,500 of its members, found that 49 per cent of Britons who holidayed in the Dominican Republic suffered from illness while there.
Other places heading the holiday destination sick-list are Mexico, Egypt, India and Sri Lanka, while visitors to Belgium and Croatia were the tourists least likely to suffer from illness, the Consumers' Association's magazine Holiday Which? found. The most common affliction is a stomach upset, accounting for almost half of all complaints, with only one in 100 travellers suffering serious illness. Holidaymakers on all-inclusive packages are twice as likely to report illness as those on room-only or half-board deals, the study concluded.
However, even before Britons board their outward flight, they are hindered by travel agents who, in most cases in the study, offered dubious destination advice, higher than necessary air fares or complacent views on safety.
Of the 240 travel agents surveyed, only 10 per cent gave correct safety advice and more than two-thirds failed to find the cheapest air fare on a particular route. Only about half came up with proper destination advice.
The agents treated operators' brochures as "divine revelation" rather than as the "glossy marketing tools they are", the report found. Patricia Yates, editor of Holiday Which?, said: "More agents are introducing service fees, yet our survey shows the level of service offered by many agents is depressingly low."
When asked to identify the cheapest possible fare between London and Paris on given dates, two-thirds of travel agents failed to do so. One came up with a fare of pounds 150 - nearly double the cost of the cheapest available fare of pounds 70.
At Going Places, only one agent out of 28 found the cheapest fare. The task of finding the best room for a quiet, relaxing family holiday by the beach in Majorca also proved too much for half of the agents. Only 24 of the agents gave the best possible advice when asked whether there were any safety issues that visitors should be aware of before booking a holiday to Jamaica.
Several agents "blithely assured" the magazine's undercover representatives that there were no safety problems in Jamaica, an opinion at odds with official Foreign Office advice. Just three agents came up with an error- free performance - Gill's Travel of Cardiff; Lunn Poly in Ashton-under- Lyne, Greater Manchester; and Z-Cars of Bristol.
Only 8 per cent of agents consulted the OAG Gazetteer, an independent source of information on accommodation and resorts known in the trade as the "truth book", the report concluded.
The countries where people fell ill the most were:
2. Dominican Republic
5. Sri Lanka
9. The Maldives