The world’s leading expert on the Inca civilisation has warned that efforts to relieve the pressure of mass tourism on Machu Picchu, the exotic, mountain-top ruin in Peru, have put other South American archeological sites at risk of destruction.

Once the preserve of backpackers on shoestring budgets, Peru has suddenly become chic, a playground for rich and famous tourists from Bill Gates, the founder of Microsoft, to Cameron Diaz, the actress.

The designation of Machu Picchu as one of “the new seven wonders of the world” earlier this year may have lifted Peru’s profile and experts worry about its capacity to cope with even more visitors.

“The infrastructure for tourism is outstripping the capacity to protect important archeological sites,” said Terence D’Altroy, professor of anthropology at Columbia University, New York.

A limit on the number of hikers allowed along the Inca trail to Machu Picchu had forced the government to find a “pressure valve”, he said.

This meant that “whole areas of archeological resources are getting visited that weren’t being visited before”.

Most at risk was Choquequirao, the “cradle of gold”, an only partially excavated Inca city that resembles Machu Picchu and is described as its “sister”.

Choquequirao is being promoted by tour operators as an alternative to Machu Picchu, the 15th-century Inca city that attracts 2,000 visitors each day, turning Cuzco, the regional capital, into one of South America’s biggest tourist destinations. The number could grow to 5,000 after the site was chosen in July as a “world wonder” by a popular vote apparently endorsed by the United Nations Fund for International Partnerships.

However, another international body, the United Nations Educational, Scientific and Cultural Organisation (Unesco), had listed Machu Picchu as an endangered world heritage site, though it withdrew this designation this year.

Sometimes Machu Picchu is so crowded that there is scarcely room to tramp around on the fragile terraces that surround buildings brought to the world’s attention when Hiram Bingham, the American explorer, stumbled across them in 1911.

“If we open up Machu Picchu to more tourism, the place will be destroyed within 10 years,” said David Ugarte, a former culture ministry official.

Yet more tourism seems inevitable. Images last week of the Hollywood actors Woody Harrel-son and Owen Wilson cavorting in an irrigation ditch in their boxer shorts near Cuzco focused attention on a part of the world that was once considered too dangerous to set foot in because of banditry and guerrilla war.

Besides Diaz, Olivia Newton-John, the singer, and Princess Beatrice have been spotted in Cuzco this year.

On a visit in June Gates attended a reenactment of Inti Raymi, or the sun festival, a colourful celebration of the winter solstice that is the most important Inca holiday.

In the 1990s tourism was complicated by war between Shining Path guerrillas and the government: in 1992, just 9,000 people visited Machu Picchu. More than 700,000 went through the turnstiles last year.

Today the guerrillas, who were inspired by Maoist doctrine, have been largely crushed and Diaz felt the need to apologise after her visit for carrying a bag that was emblazoned with a red star and the Maoist slogan “serve the people” printed in Chinese on the flap.

Unesco says the site is in good condition except for the main stone shrine, which was chipped when a crane fell during the filming of a beer advertisement.

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