OPZZ leader Jan Guz said the march was a warning and if the government does not change its policies "we will block the whole country, we will block every highway, every road" to demand better work conditions.
"We don't accept a policy that leads to poverty," Guz said amid the noise of whistles and horns.
Poland has experienced big strikes in the past. In the 1980s, the Solidarity freedom movement organized nationwide strikes that eventually led to democratic reforms.
A prominent member of Tusk's Civic Platform party, Rafal Grupinski, said the workers have every right to express their discontent, but they should primarily return to the long-established negotiations with the government and employees, which they broke off in the summer over changes to the labor code.
The marchers complained of large-scale layoffs after economic growth slowed down to 1.9 percent of gross domestic product last year from 4.5 percent in 2011. They want job security and contracts that guarantee health care and retirement benefits at a time when unemployment is at 13 percent and many companies offer short-term contracts without social security.
Workers say average monthly wages of about 3,700 zlotys ($1,150) before tax are among Europe's lowest. They also want the reversal of a recent raise in the retirement age to 67 years from the previous 60 years for women and 65 years for men.
The ruling coalition of Tusk's center-liberal party and a peasant party is losing popularity to the nationalist opposition Law and Justice party of former prime minister, Jaroslaw Kaczynski, and its parliament majority has shrunk precariously to 232 votes in the 460-member lower house.