European Commission President Jose Manuel Barroso attacked Bulgaria's thriving culture of corruption and organised crime Friday but backed its prime minister's efforts to root them out.

"High-level corruption and organised crime have no place in the European Union and cannot be tolerated," Barroso said after talks with Prime Minister Sergey Stanishev.

"It is a question of public confidence that those who break the rule of law are not above the rule of law," he added.

Barroso arrived on a one-day visit to Sofia on Friday amid a high-level corruption scandal that has shaken Stanishev's centre-left government.

Tapped phone calls leaked to the press earlier this week exposed alleged links between top crime-busters and criminals under investigation.

Stanishev has also come under pressure from the right-wing opposition to sack his powerful Interior Minister Rumen Petkov.

"It remains a source of frustration that some in Bulgaria are determined to undermine the reforms that need to be made," Barroso said in a stern warning, fully backing Stanishev's "strong line" and his "full commitment to reforms."

"Honestly, we expect more concrete results in terms of the fight against organised crime and corruption. And it is important that all the institutions of the state cooperate in that direction," Barroso said.

"We cannot be all the time repeating that more needs to be done... Endless investigations, delayed court cases do not amount to justice," he added.

Bulgaria joined the European Union in 2007 but continues to face strong criticism from Brussels for failing to root out high-level corruption and put well-known criminal bosses behind bars.

Corruption concerns also prompted Brussels recently to partly freeze pre-accession subsidy payments of at least 450 million euros still due to the EU newcomer, .

That should be seen as a "wake-up call," Barroso said, implying that more EU funds might be frozen if corruption is not stamped out.

"No-one is more interested in solving these issues than the Bulgarian government and the people," Barroso said.

Barroso also met Friday with President Georgy Parvanov and was awarded the highest Bulgarian state order for his support for the country's European accession and his role in freeing six Bulgarian medical workers from eight-year imprisonment in a Libyan AIDS trial.

Bulgaria currently ranks 64th in the world according to the Transparency International "Global Corruption Perception Index", an academic tally of corruption data and opinion polls on perceived state and corporate bribery.