In a worst-case scenario - a disorderly break-up of the euro zone - Euromonitor said the number of tourists arriving in the bloc's countries would drop by as much as 11 percent amid a sharp recession and the resultant hit to the world economy.

Spending by tourists would decline at an even faster rate of as much as 17.3 percent, as consumers seek out bargains and lower demand weighs on prices, it said in a report basing its findings on a review of previous economic downturns in times of macroeconomic instability.

A less severe scenario than a complete euro-zone breakup would be an exit of Greece, while the rest of the bloc remains intact, causing a 2.8 percent decline in the number of tourist arrivals in the region, Euromonitor estimated.

If neither scenario comes to pass, euro-zone tourist arrivals will likely decline by 0.7 percent this year, it said.

Greeks face a cliffhanger election on Sunday that many fear will result in the country, which relies on tourism for about a fifth of its economic income, being forced out of the euro.

Some have said Greece would benefit from an exit from the euro zone, after a 15 percent drop in tourism income in the first quarter of 2012.

British tour operator Thomas Cook (TCG.L) for instance, which competes with TUI Travel (TT.L) among others, said last month it expects a surge in bookings to Greece if it leaves the euro zone, as holidays to the Mediterranean nation would become better value.

In a total collapse of the euro zone, hotels could see revenues drop by 15 percent. They would also be hit by a lack of bank lending, leaving independent hotels with no source of funding for investments and making them potential takeover targets for budget chains, Euromonitor said.

Spending on plane tickets would drop by almost 20 percent as companies slash travel budgets and tourists cancel their travel plans or switch to trains and buses to save money.

"The macroeconomic impact of a euro zone disintegration would be catastrophic," it said.

However low-cost carriers such as Ryanair (RYA.I) and easyJet (EZJ.L) would suffer much less than flag carriers such as Deutsche Lufthansa (LHAG.DE) or British Airways (ICAG.L), though, as they snap up increasingly cost-sensitive passengers.

(Reporting by Maria Sheahan; Editing by David Holmes)

• A Permanent Economic Emergency