Demonstrators accuse Borissov and the country's top prosecutor, Ivan Geshev, of corruption, authoritarian rule and dependence on criminal groups. They are calling for both men to step down.
Bulgaria's centre-right government survived a vote of no confidence on Tuesday despite anti-corruption protests calling for the ousting of Prime Minister Boyko Borissov.
The vote was the fifth one called by the opposition socialist party (BSP).
It was defeated by 124 votes to 102 with 11 abstentions and three lawmakers absent.
Protests against the government have been ongoing for over two weeks. Demonstrators accuse Borissov and the country's top prosecutor, Ivan Geshev, of corruption, authoritarian rule and dependence on criminal groups. They are calling for both men to step down.
Borissov, in power since 2009, has refused to step down before the end of his third term in March 2021. He attempted to quell the unrest last week by sacking three of his top ministers.
BSP chair Korneliya Ninova said in a statement after the ballot that the vote showed "that Borissov's government and its associate parties will deny the reality in the name of power until the very end at any cost".
"This parliament is delegitimised and it doesn't represent the majority of the Bulgarian citizens and their desire for change. In our opinion the next steps should be the dissolution of the parliament and a call for new elections," she also said.
Cabinet reshuffle and elections
According to Andrius Tursa, Central & Eastern Europe Advisor at Teneo Intelligence, "the probability of snap polls is rising" due to the ongoing protests which he described as the largest since 2013.
"The political situation will remain unstable," he wrote in a note released on Tuesday, adding that Borissov could also announce a more radical cabinet reshuffle within the coming days although he cautions that the move would be unlikely to curb discontent.
"Borissov might be tempted to go to the polls early, as his key opponents are largely unprepared for this and the economic situation is expected to deteriorate in the coming months.
"Such a scenario would become more likely if protests do not abate," he went on.
Vessela Tcherneva, deputy director of the Sofia office of the European Council for Foreign Affairs (ECFR) think thank concurred.
"There will be a major reshuffle of government (which some of the opposition may consider satisfactory as they are not prepared for elections) and a credible promise of early elections," she told Euronews.
She added that the BSP is "trying to create momentum through no-confidence votes but they haven't succeeded — neither this time nor before".
"The Socialist Party has been a weak and passive opposition all along. It has been involved with the same oligarchs and corruption practices in the past so it is difficult for BSP to be a credible part of the protest," she added.
Corruption is the government's 'trademark'
Justice for All, which promotes reform to the judiciary, is among the organisations taking part in the protests.
In a statement to Euronews, they said "corruption and trading in influence have become a government trademark in the last decade".
They denounced the alleged influence wielded behind the scenes by two oligarchs: Ahmed Dogan, the former leader of the MRF Turkish minority party, and Delyan Peevski, a powerful businessman and pro-government media owner.
They described the judiciary as "inefficient, dependent on politicians and largely oppressed by the powerful figure of the Prosecutor General" and said Geshev has neither "the necessary professional and moral qualities to hold such a key state office".
According to the NGO, Geshev has been "selectively publishing pieces of evidence from investigations and pre-trial recordings contrary to all basic principles of criminal procedural law and the presumption of innocence."
Justice for All has been calling for Geshev resignation since last year but was buoyed recently by raids by armed police and prosecutors in the office of two of close aides of President Ruman Radev, who is backed by the BSP.
"The feeling of state capture by the oligarchy charged our protests with a fresh and strong energy. Our task is one — to reclaim our country," they added.
Bulgaria is the most corrupt country in the European Union, according to watchdog Transparency International.
The NGO has placed the country last in a ranking of EU countries for seven consecutive years and flagged that there has been "no significant progress in fighting corruption in comparison with other countries from the EU" between 2012-2019.