Bulgaria's parliament passed anti-corruption legislation on Wednesday under European Union pressure over its failure to prosecute venal officials, but President Rumen Radev has said the bill is not fit for purpose and he will veto it.

The Balkan, formerly communist country is the poorest as well as one of the most corrupt countries in the EU, which it joined in 2007, and has made scant progress towards stamping out graft and organised crime.

Radev said the new five-person unit, meant to investigate persons occupying high state posts as well as assets and conflict of interest, may not be truly independent

The European Commission, the EU's executive, has repeatedly rebuked Bulgaria for failing to prosecute and sentence allegedly corrupt officials and for not overhauling a creaking judiciary.

"This law corresponds to the wishes of Bulgarian citizens and the European Commission," said Tsvetan Tsvetanov, chairman of the ruling GERB party's parliamentary group.

Analysts voiced concern, though, that the bill would not allow efficient investigations of corruption networks.

The management of a special anti-graft unit envisaged by the legislation would be appointed by parliament, something analysts said could limit its objectivity.

Radev said the new five-person unit, meant to investigate persons occupying high state posts as well as assets and conflict of interest, may not be truly independent and could be used by those in power to persecute opponents.

"The instruments envisaged in this law are ineffective," Radev said last week. "It does not deal a blow on those who feed corruption, and it can be used as a weapon against inconvenient people." He said he would veto the measure.

The president, prime minister and lawmakers could be targets of investigation, as well as municipal councillors, directors of hospitals and border customs bosses.

The new law also focuses on improving control and accountability of law-enforcement agencies, just before Bulgaria assumes the six-month, rotating EU presidency in January.

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