Updated

Bulgaria's biggest political party said Tuesday it was boycotting parliamentary sittings amid unrelenting public outrage over the appointment of a media magnate to a top security post.

The decision by the conservative opposition GERB party added pressure on the three-week-old ruling coalition, and fuelled fears of a new political crisis as anti-government street protests stretched into a fifth straight day across Bulgaria.

"We will not show up in parliament anymore," GERB leader and former prime minister Boyko Borisov said.

Thousands of Bulgarians have poured onto the streets in the EU's poorest country since Friday to protest the controversial appointment of the inexperienced but well-connected lawmaker Delyan Peevski as chief of the powerful DANS security agency.

Peevski is understood to be behind a media empire of newspapers and a television, officially owned by his mother.

Even though Prime Minister Plamen Oresharski has reversed the decision, protesters have not been appeased. Instead, public anger has boiled over into protests against the government.

The demonstrations come just months after anti-poverty rallies brought down Borisov's government in end-February.

Some 7,000 people took to the streets in Sofia on Tuesday, demanding the resignation of Oresharski's technocrat government.

"The situation is such that Oresharski has to go. Nobody will accept anything other than a resignation," bank clerk Hristo Tsvetkov, 38, told AFP while waving a Bulgarian flag at a rally.

Oresharski, who drew ire through his nomination of Peevski, has so far refused to step down.

While rejecting the prime minister, protesters said Borisov's return to power was also not an option.

"It's utter stalemate and won't be resolved by new snap elections which will re-create the current situation in parliament and send us back on the streets again," Tsvetkov said.

The demonstrators are now pressing for changes to the electoral code which they believe would bring new faces to politics and remove an establishment viewed as corrupt and easily swayed by powerful business interests.

The changes sought also included making it easier for smaller parties to enter parliament and relaxing the rules for independent candidates to stand for election.

The Socialists said they were ready to put the changes to debate in parliament and met Tuesday with representatives of 60 civil groups to hear their demands.

Despite the boycott, GERB said they would return to parliament for sessions dealing with the new electoral code if this was what the people wanted.

Oresharski's cabinet was formed after inconclusive snap elections on May 12, as GERB, which won 97 out of 240 seats in parliament, failed to find partners to form a government.

The current coalition is backed by the Socialists and Peevski's Turkish minority MRF party, which have a combined majority of 120 seats.

The highly unpredictable ultra nationalist party Ataka has also hinted it was ready to give the cabinet its silent backing by abstaining in key votes.

Parliament requires a quorum of 121 lawmakers to pass legislation, which means it can still function without GERB.