Islamist attacks have scared off thousands of tourists from Paris and its top attractions, helping rob the region of about 750 million euros ($850 million) in revenues, officials said on Tuesday.
Strikes and floods have also taken their toll, overshadowing the boost from the Euro 2016 soccer championships and leaving the tourism industry in need of massive new investment and a rescue package, they added.
"It's time to realize that the tourism sector is going through an industrial disaster," the head of the Paris region tourist board, Frederic Valletoux, said in a statement.
Visitors to the Arc de Triomphe fell more than a third in the first half of 2016 from the same period a year earlier, the board added.
The Grand Palais museum reported a 43.9 percent slump and the Palace of Versailles, outside the city, just short of 20 percent.
"Hotels are already laying off staff though they're not saying it. This industry is on its knees and it needs relief measures now. Hoteliers need the arms to fight back," Georges Panayotis, head of hotel research firm MKG group, told Reuters.
Hotel revenues were down 15 percent this summer in the Paris region, he said. Wealthier tourists were staying away in even greater numbers, with high-end hotels reporting of declines of between 30-40 percent.
Targeted VAT cuts and other tax breaks could be part of the answer, he added.
Tourism typically provides more than 7 percent of France's gross domestic product, at a time when the country is trying to boost its economy.
But it has had to contend with a series of disasters, from Islamic State attacks that killed 130 people in Paris last year to the carnage when a gunman drove a truck into crowds celebrating Bastille Day in the Riviera city of Nice this July.
"The Nice attack derailed our hopes of a recovery. It's a dramatic situation and there will be job cuts in the sector if things do not get better by the end of the year," Christian Navet, head of the UMIH-Paris-Ile-de-France hotel federation, said.
The numbers of Japanese visitors had almost halved in the first half of the year from last, according to tourist board figures. Russians had fallen by more than a third and Chinese by almost a fifth.
Weak activity in France contributed to a fall in first-half operating profit for French group AccorHotels. Air France-KLM has said it expects its unit revenues to decline in July and August, partly due to the situation in France.
Only massive new investments would help to protect jobs in the sector, said the tourist board's Frederic Valletoux, urging Foreign Minister Jean-Marc Ayrault to meet with local tourism officials.
"This is no longer the time for communication campaigns but to set up a relief plan," he added.