"Despite optimistic forecasts, activity has been down since June, many professionals have seen their revenue fall by 30% compared with previous years," a group of restaurant, hotel, retail and nightspot unions said in a joint statement.
Their businesses are suffering from tourists avoiding the capital, unfavorable weather, inflation, a tense political situation after President Emmanuel Macron called snap elections, and the Olympic security measures, they said.
Combined, the headwinds are producing "disastrous economic consequences", they said.
The unions urged authorities to communicate more clearly in particular about the security measures, saying they were unable to plan around them without information.
One example was the Trocadero square near the Eiffel Tower in western Paris, where restaurants are "suffering access restrictions that have sent footfall plunging by 70%," they said.
Elsewhere, security barriers blighting otherwise picturesque streets in the capital are driving prospective customers away, the unions charge.
"Many small businesses risk shuttering for good," they said, calling for the government to set up compensation procedures.
"We insist that fair and swift compensation is necessary to make up for the inconvenience and losses suffered because of the Olympic Games," the unions said.