Bus drivers cruised the streets of Poland's second-largest city with horns blaring and flags waving in a "hunger demonstration" today as the independent Solidarity union federation came under mounting pressure from its own supporters to stage strikes over widespread shortages of food and other everyday needs.

Telex messages flooded into Solidarity offices around the country from factories calling for vigorous protests against inadequate supplies of food, detergents, and medicines. The outpouring came against the backdrop of a government statistical report on the past six months showing that the economy has entered a gradual process of collapse with significant drops in almost all fields of production.

Solidarity is attempting to steer the discontent, announcing its own demonstrations and setting up a special six-member task force under union leader Lech Walesa to negotiate with the Communist authorities. But union officials fear the uncorrdinated local protests could get out of hand unless food supplies improve in the near future.

For the second day running, Solidarity activists in Lodz, the country's second-largest city, staged their own protest. Employes of the local transport company who drove through the streets centered their complaints on a chronic shortage of meat.

The protests reach a climax Thursday when women and children plan to march through the city. The women, many of whom are employed in the textile industry, complain that they sometimes have to wait in line for up to 24 hours to buy their meat ration.

Threats of strikes were also reported from the nearly town of Piotrkow Tybunalski and the southern industrial city of Czestechowa. In the northern port of Gdansk, the scene of massive strikes last year, Solidarity members have been told not to pick up their monthly ration cards for August entitling them to 6.6 pounds of meat.

Most Polish economists believe there is little prospect of meat supples improving dramatically in the next few months. While this year's grain crop is expected to be good thanks to prolonged sunny weather, livestock herds have been run down and will take time to build up.

Emergency food supplies are beginning to arrive from abroad, including the United States, but still represent only a small proportion of Poland's needs. With declining exports and a hard currency debt of $27 billion, Poland has no money to pay for food imports.

The downward economic spiral was illustrated by the government's statistical report showing that exports had fallen 23 percent over the past year and imports 16 percent. Apartment building was down 30 percent, purchases of livestock from private farmers 23 percent and coal production 22 percent.

Coal exports, traditionally Poland's biggest single hard currency earner, were down to 8.5 million metric tons in the first six months of this year from 19.5 million in the same period last year.

Poland's primary economic problem is that, deprived of hard currency earnings, it cannot afford to buy essential raw materials and spare parts to keep its industry going. This has caused widespread production losses and created chronic shortages of practically every basic consumer item from cigarettes to detergents to matches.

The decline was also reflected in a small news item announcing that Warsaw public transport will soon have to drastically reduce its services because of a lack of tires and spare parts. More than 375 trams and 300 buses are already idle and, over the next week, the remainder could run out of motor oil and brake fluid. Public transport has already been cut back in several major cities including Lodz.

Meanwhile, a dispute regarded as a test case of workers' rights to elect their own director has been temporarily resolved. Under a compromise reached last week, the workers' choice for director of the state airline Lot will become commercial manager and first deputy director. He will share power with the government's appointment as director, an Air Force general.