PARIS -- For months Parisians have been alternately fuming and grinning about the growing number of cars cutting through city traffic with sirens wailing and blue lights blinking.

There was nothing to be said about an ambulance speeding toward the hospital, of course, or a carload of determined policemen heading to the scene of a crime. As residents of a world capital, Parisians also have grown used to sirens and flashing lights for important visitors rushing to and from the airport.

But it was those relaxed sets of functionaries flashing and blaring their way down the busy streets about midday that raised the questions.

"There they go, off to lunch," someone inevitably would sneer from the back of the bus.

Finally, even Prime Minister Jacques Chirac had enough, and told his ministers so. "I am irritated by the inflation of convoys protected by motorcycles that drive through Paris with great blowing of sirens and flashing of lights, and that cause traffic difficulties and exasperate the population," the prime minister said recently.

Chirac added that, "at the request of the mayor of Paris," he has handed down orders to his government strictly limiting use of sirens and flashing lights to emergencies and foreign heads of state. He was all the more willing to comply with the request because, in addition to being prime minister, Chirac is mayor of Paris.

PRESIDENT FRANCOIS MITTERRAND had to say it again yesterday, on the French national day, just after the troops marched triumphantly down the Champs Elysees and the jets roared overhead spewing out smoke in the national colors. Don't worry, he told a nationwide television audience, France is not in decline.

Mitterrand had said it before, but apparently thought it bore repeating. Chirac also has said it before, making it one of the few subjects on which the two rivals agree.

The reassurances were considered necessary because somewhere in the swirl of Parisian intellectual fashion, it had been decided that the country is going to pot. Over $50 lunches, Frenchmen in the know suddenly were discussing whether the slide could be arrested in time.

No one knows for sure how the idea got started. But a business executive's book this spring called "Lazy France" popularized the disparagement theory. Author Victor Scherrer argued that with five weeks' paid vacation, a 39-hour work week and 10 legal holidays, French men and women put in too little time on the job.

A magazine survey, taken as a spate of articles appeared on the subject, showed 56 percent of the population believe France is indeed generally on the decline and 67 percent believe its industry is declining compared to the rest of the world.

On top of that, the respected National Institute for Statistics and Economic Studies issued new figures predicting a slowing of economic growth, rising unemployment and inflation, and a foreign trade imbalance falling farther into the red.

"The hit of the summer," headlined the weekly magazine Figaro in an article on what by then had been baptized "The Decline."

Government economists swiftly pulled out statistics proving that the French work longer than West Germans, harder than Britons and better than just about anybody else. Unsaid but firmly in politicians' minds was a fear that "the decline of France" could be a powerful political theme in the hands of a candidate in next year's presidential elections, particularly one who is not now in the government.

"This is the tune of the moment," a senior official sniffed. "But Frenchmen, being creatures of fashion, will be tired of it by election time."

DECLINE OR NOT, France has already started its summer holidays.

Tradition has it that Parisians all leave together in August, abandoning the city to tourists, and then return in a single mad traffic jam on Sept. 1. For those able to pick up the fine waves of what is in and what is out, however, an advanced schedule is becoming chic, making departure in mid-July a must and presence in Paris at the end of August equally a sign of social standing.

A high government official tells a recent visitor he is leaving on vacation this week, but to drop by and see him next month, saying confidently: "I'll be right here in my office from Aug. 15 on."

Similarly, a stylish intellectual explains that nobody who is anybody would be around Paris for a cocktail party at the end of July, while everybody would be available at the end of August.