Bulgarian President Rumen Radev vetoed anti-corruption legislation approved by parliament last month, saying it doesn’t do enough to counteract graft as the Balkan country assumes the European Union’s rotating presidency.

The law, passed in an effort to improve the nation’s image as the EU’s most-corrupt member, doesn’t clearly define institutions’ responsibilities and doesn’t protect whistle-blowers from prosecution, Radev said Tuesday by email. He urged lawmakers to expand the law’s scope to investigate public officials and their activities.

Radev acted only a day after Bulgaria, the European Union’s poorest country, assumed the six-month, rotating presidency of the bloc for the first time since it joined the EU in 2007.

The European Commission has been urging Bulgaria to reform its judicial system and step up the fight against organized crime since the country joined the EU a decade ago. Failure to do so has caused some member states to reject Bulgaria’s bid to join the Schengen passport-free travel zone, even after it met the area’s technical requirements. Transparency International ranks Bulgaria the EU’s worst nation for corruption in its 2016 perceptions index.

Bulgaria has made scant progress towards stamping out graft and organized crime, and the European Commission, the EU’s executive, has repeatedly rebuked the Black Sea country for failing to prosecute and sentence allegedly corrupt officials.

The legislation, approved by parliament on Dec. 20, entailed the creation of a special anti-graft unit meant to investigate persons occupying high public office as well as assets and conflicts of interest.

But analysts said the unit’s objectivity could be limited by the fact its management would be appointed by parliament under the legislation, and it therefore might not be truly independent and could by used by those in power to persecute opponents.

“I believe that the adopted law not only does not create an adequate legal basis for tackling corruption but will even make it difficult to fight it,” Radev, who was elected in November 2016, said in a statement.

Some analysts, however, expect parliament to overturn Radev’s veto.

The new law also focuses on improving control and accountability of law-enforcement agencies, and the government in Sofia is hoping Bulgaria will be able to change opinions and remove its tarnished image during its EU presidency.

Corruption has deterred foreign investment since communism collapsed in Bulgaria in 1989, and the EU has kept Sofia as well as neighboring Romania – for the same rule-of-law failings – outside its Schengen zone of passport-free travel.