When the head of the Bulgarian roads agency was forced to resign in February after handing contracts worth €50 million (£40 million) to his brother, it confirmed the worst fears of those who doubted the country’s suitability for EU membership.

Corruption and organised crime seem endemic in the Black Sea state, which stands to gain ¤11 billion in development funds from Brussels over the next seven years after being allowed to join last year.

But despite repeated promises from the Socialist Government of Sergei Stanishev to guarantee financial and legal probity, patience is wearing thin among fellow EU members. Since 2000 Bulgaria has had 150 mafia-style killings but not one conviction.

In an interview with The Times, Mr Stanishev, 42, admitted that his Government had relaxed its drive to reform after a frantic year preparing for membership, but he pledged to redouble efforts to clean up the country and safeguard its EU windfall.

“The Government and parliament worked without any summer or winter holidays the year before our accession, because it was very important to prove to ourselves as a nation that Bulgaria, when mobilised, can achieve goals,” Mr Stanishev said.

“Somehow there was a kind of relaxation mentality: ‘We did everything well, we can relax’, and this is a very substantial part of the problem now.”

The former journalist, who was a student at the London School of Economics, has been forced into action by signs that the European Commission has now started to lean on his administration, despite warnings that too much pressure could bring down his fragile coalition.

This month Brussels demanded 25 changes by June 16 to the way that Bulgaria handled EU funds and froze about €400 million of aid.

In response Mr Stanishev created an independent police force of officers on elevated salaries in an effort to make them mafia-proof. He also dismissed Rumen Petkov, the long-standing Interior Minister, after a parliamentary report linked him to organised crime suspects and criticised his ministry for leaking sensitive files.

Meglena Plugchieva, the respected Bulgarian Ambassador to Germany, has returned as Deputy Prime Minister to enforce the demands from the EU. Mrs Plugchieva said: “We have exactly one month to pull ourselves together, concentrate our efforts and perform a huge number of tasks to present the commission with evidence that we have at least begun to address the areas of concern.”

Despite the claim by Mr Stanishev that if any politician “does not have the confidence of our European partners, he will have to leave his place” eyebrows were raised when a Cabinet reshuffle this month did not move Asen Gagauzov, the Minister of Regional Development and Public Works, who gave the roads agency a clean bill of health in a review.

Mr Gagauzov said: “I am not worried that organised crime will have access to European funds because it is no different here to organised crime in other parts of the world. It is to do with drug trafficking and prostitution — it is nothing to do with European funds.”

The stakes are high, not just for Brussels where “enlargement fatigue” after misgivings over Bulgaria and Romania is damaging the accession chances of Croatia and other Balkan countries, but also for Mr Stanishev, who faces a general election next year against a popular right-wing Opposition.

The problem for the Prime Minister is that every advance in finding corruption reveals fresh cases. “We do have problems in corruption and organised crime, no one denies it,” he said. “But Bulgaria has made a revolution and if you look at economic development, it is a success story.”

Bulgaria, bribery and the EU budget

— Bulgaria cut unemployment and controlled inflation under King Simeon II, right, Prime Minister from 2001-05

— Bulgaria joined the EU last year under a corruption-monitoring scheme

— Between 2001-06 150 people were killed in Sofia, the capital. Victims included Bulgaria's top banker, a football company boss and one of its top importers

— This year the EU froze subsidies of more than £79 million over bribery in the construction of a motorway

— The European Commission's total budget for Bulgaria for 2007-13 is about £7 billion

— By March the EU's investigating agency had 45 cases of alleged malpractice in Bulgaria on its books

Sources: Transparency International, Times archives

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