Fresh protests kicked off Saturday in Warsaw, with several thousand demonstrators waving Polish flags, blasting air horns and chanting "Stop the devastation of Poland".
They marched to the heavily guarded parliament building to voice anger at the governing rightwing Law and Justice (PiS) party and measures including its plans to impose new restrictions on media coverage of the chamber.
"I don't want to see Poland turned upside down" by the PiS, a protester in her 60s, Malgorzata Kramarz, told AFP on Saturday.
She was referring to the controversies over government action on several issues ranging from tightening the abortion law to changes to Poland's constitutional court's decision-making rules, which sparked a crisis.
Opposition anger boiled over on Friday with dozens of Polish MPs seizing parliament's main chamber over the plans to restrict journalists, as thousands of demonstrators marched outside in support for their stance.
The speaker of parliament had to interrupt the session and hours later transferred the proceedings to another gallery so lawmakers could vote on the state budget for 2017.
The quorum for the vote was met, though the opposition slammed it as illegal.
Meanwhile the protesters blocked the exits of the parliament building, with Prime Minister Beata Szydlo and PiS party chief Jaroslaw Kaczynski only managing to leave the building overnight by forcing their vehicles through the crowd with the help of police.
'Violation of the law'
The restrictions planned by the conservative party grant access to the parliament's press gallery to only two journalists per outlet, and ban them from shooting still pictures or video.
The limits prevent the media from recording images of lawmakers when they break the rules, for example by voting for an absent colleague.
The PiS has defended the measure, saying it seeks to ensure a comfortable work environment for both lawmakers and journalists.
"It's definitely not meant to reduce transparency," PiS lawmaker Arkadiusz Mularczyk said previously.
On Saturday the main opposition parties announced they would seek an investigation into the budget vote, while dozens of lawmakers remained in the chambers and pledged to remain until next week.
The prime minister's spokeswoman denounced "a violation of the law", referring to the opposition's taking over of the parliament chambers.
Emerging from a long silence, Poland's President Andrzej Duda called for calm, expressing his "worry" over the turmoil and offering to mediate.
European Union President Donald Tusk, a former Polish premier, called on the government during a ceremony in Warsaw to respect "the people as well as the principles and values of the constitution".
"When we deprive people of access to information or when we impose a single way of living, democracy becomes as unbearable as a dictatorship," he said.
The battles PiS has fought since coming to power about a year ago have not undermined its support, with the latest polls giving it a roughly 35 percent approval rating. That score beats the combined ratings of the two main opposition parties.
The government's success is due in part to its flagship project, a child allowance programme that gives families a monthly 500 zlotys ($120, 112 euros) for every child after the first.